Exploring the influence of atomic level structure, porosity, and stability of bismuth(iii) coordination polymers on electrocatalytic CO2 reduction

2021. Sara Frank (et al.). Journal of Materials Chemistry A 9 (46), 26298-26310

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Bismuth-based coordination polymers (CPs) have recently attracted attention as catalyst precursors for the electrocatalytic CO2 reduction reaction (eCO(2)RR). We present a comparative study by investigating six bismuth-based compounds in-depth to elucidate the correlation between their structures and their catalytic CO2-to-formate conversion. Thereby, we identify structural indicators of the pristine CPs resulting in optimized catalytic performance, paving the way for future design of CP derived catalysts. The structural properties of the six pristine materials vary in terms of porosity (from non-porous to 495 m(2) g(-1)), linker type (carboxylate- or phenolate-based), thermal- and chemical stability, and metal content. Herein, electrochemical studies are combined with comprehensive structural investigations using electron microscopy, powder X-ray diffraction, and X-ray absorption spectroscopy. Our study reveals that low chemical stability of the pristine CPs is crucial for the conversion of the precursors into active Bi2O2CO3 and of paramount importance for the eCO(2)RR activity, while the nature of the pristine material mostly influence the catalyst morphology and transport properties. Of the six investigated CPs, the best performing compounds selectively convert CO2 to formate with faradaic efficiencies in the range 80(3)-95(3)% and current densities of 5(1)-8(1) mA cm(-2) at -0.97 V-RHE.

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Toward Sustainable Li-Ion Battery Recycling

2021. Jędrzej Piątek (et al.). ACS sustainable chemistry and engineering 9 (29), 9770-9778

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The growing demand for Li-ion batteries (LIBs) has made their postconsumer recycling an imperative need toward the recovery of valuable metals, such as cobalt and nickel. Nevertheless, their recovery and separation from active cathode materials in LIBs, via an efficient and environmentally friendly process, have remained a challenge. In this work, we approach a simple and green method for the selective separation of nickel ions from mixed cobalt-nickel aqueous solutions under mild conditions. We discovered that the bioinspired microporous metal-organic framework (MOF) SU-101 is a selective sorbent toward Ni2+ ions at pH 5-7 but does not adsorb Co2+ ions. According to the Freundlich isotherm, the adsorption capacity toward Ni2+ reached 100.9 mg.g(-1), while a near-zero adsorption capacity was found for Co2+ ions. Ni2+ removal from aqueous solutions was performed under mild conditions (22 degrees C and pH 5), with a high yield up to 96%. The presence of Ni2+ ions adsorbed on the surface of the material has been proven by solid-state H-1 nuclear magnetic resonance spectroscopy. Finally, the separation of Ni2+ from Co2+ from binary solutions was obtained with approximately 30% yield for Ni2+, with a near-zero adsorption of Co2+, which has been demonstrated by UV-vis spectroscopy. The ion adsorption process of Ni2+ and Co2+ ions was additionally studied by means of classical molecular dynamics calculations (force fields), which showed that the Ni2+ ions were more prone to enter the MOF canals by replacing some of their coordinated water molecules. These results offer a green pathway toward the recycling and separation of valuable metals from cobalt-containing LIBs while providing a sustainable route for waste valorization in a circular economy.

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Metal-Dependent and Selective Crystallization of CAU-10 and MIL-53 Frameworks through Linker Nitration

2021. Timo Rabe (et al.). Chemistry - A European Journal 27 (28), 7696-7703

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The reaction of the V-shaped linker molecule 5-hydroxyisophthalic acid (H2L0), with Al or Ga nitrate under almost identical reaction conditions leads to the nitration of the linker and subsequent formation of metal-organic frameworks (MOFs) with CAU-10 or MIL-53 type structure of composition [Al(OH)(L)], denoted as Al-CAU-10-L-0,L- 2,L- 4,L- 6 or [Ga(OH)(L)], denoted as Ga-MIL-53-L-2. The Al-MOF contains the original linker L-0 as well as three different nitration products (L-2, L-4 and L-4/6), whereas the Ga-MOF mainly incorporates the linker L-2. The compositions were deduced by H-1 NMR spectroscopy and confirmed by Rietveld refinement. In situ and ex situ studies were carried out to follow the nitration and crystallization, as well as the composition of the MOFs. The crystal structures were refined against powder X-ray diffraction (PXRD) data. As anticipated, the use of the V-shaped linker results in the formation of the CAU-10 type structure in the Al-MOF. Unexpectedly, the Ga-MOF crystallizes in a MIL-53 type structure, which is usually observed with linear or slightly bent linker molecules. To study the structure directing effect of the in situ nitrated linker, pure 2-nitrobenzene-1,3-dicarboxylic acid (m-H2BDC-NO2) was employed which exclusively led to the formation of [Ga(OH)(C8H3NO6)] (Ga-MIL-53-m-BDC-NO2), which is isoreticular to Ga-MIL-53-L-2. Density Functional Theory (DFT) calculations confirmed the higher stability of Ga-MIL-53-L-2 compared to Ga-CAU-10-L-2 and grand canonical Monte Carlo simulations (GCMC) are in agreement with the observed water adsorption isotherms of Ga-MIL-53-L-2.

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Isoreticular Chemistry of Group 13 Metal-Organic Framework Compounds Based on V-Shaped Linker Molecules

2021. Timo Rabe (et al.). Inorganic Chemistry 60 (12), 8861-8869

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Following the concept of isoreticular chemistry, we carried out a systematic study on Ga-containing metal–organic frameworks (MOFs) using six V-shaped linker molecules of differing sizes, geometries, and additional functional groups. The linkers included three isophthalic acid derivatives (m-H₂BDC-R, R = CH₃, OCH₃, NHCOCH₃), thiophene-2,5-dicarboxylic acid (H₂TDC), and two 4,4′-sulfonyldibenzoic acid derivatives (H₂SDBA, DPSTA). The crystal structures of seven compounds were elucidated by a combination of model building, single-crystal X-ray diffraction (SCXRD), three-dimensional electron diffraction (3D ED), and Rietveld refinements against powder X-ray diffraction (PXRD) data. Four new Ga-MOFs that are isoreticular with their aluminum counterparts, i.e. Ga-CAU-10-R (Ga(OH)(m-BDC-R); R = OCH₃, NHCOCH₃), Ga-CAU-11 (Ga(OH)(SDBA)), and Ga-CAU-11-COOH (Ga(OH)(H₂DPSTC)), were obtained. For the first time large single crystals of a MOF crystallizing in the CAU-10 structure type could be isolated, i.e. Ga-CAU-10-OCH₃, which permitted a detailed structural characterization. In addition, the use of 5-methylisophthalic acid and thiophene-2,5-dicarboxylic acid resulted in two new Ga-MOFs denoted Ga-CAU-49 and Ga-CAU-51, respectively, which are not isostructural with any known Al-MOF. The crystal structure of Ga-CAU-49 ([Ga₄(m-HBDC-CH₃)₂(m-BDC-CH₃)₃(OH)₄(H₂O)]) contains an unprecedented rod-shaped inorganic building unit (IBU) of the formula _∞¹{Ga₁₆(OH)₁₈O₆₀}, composed of corner-sharing GaO₅ and GaO₆ polyhedra. In Ga-CAU-51 ([Ga(OH)(C₅H₂O₂S)]) chains of alternating cis and trans corner-sharing GaO₆ polyhedra form the IBU. A detailed characterization of the title compounds was carried out, including nitrogen gas and water vapor sorption measurements. Ga-CAU-11 was the only compound exhibiting porosity toward nitrogen with a type I isotherm, a specific surface area of a_S,BET = 210 m²/g, and a micropore volume of V_mic = 0.09 cm³/g. The new MOF Ga-CAU-51 exhibits exceptional water sorption properties with a reversible S-shaped isotherm and a high uptake around p/p₀ = 0.38 of m_ads = 370 mg/g.

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3D electron diffraction as an important technique for structure elucidation of metal-organic frameworks and covalent organic frameworks

2021. Zhehao Huang (et al.). Coordination chemistry reviews 427

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Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have emerged as the most widely investigated classes of porous materials during the past two decades. The almost unlimited combination of building units (metal clusters and organic molecules) endows highly tuneable porosities and functionalities that are appealing for a wide scope of applications. The applications of MOFs and COFs depend on their physical and chemical properties, which in turn are determined by the arrangement of atoms - the crystal structures. Therefore, structure determination is arguably the most important characterization step for MOFs and COFs. While single crystal X-ray diffraction (SCXRD) is the most widely used method for structure determination, many MOFs and COFs are synthesized in too small sizes or their crystal qualities are too low for SCXRD. During recent years, three-dimensional electron diffraction (3DED) methods has undergone rapid developments and can be used for structure determination of nano- and submicro-sized crystals to overcome this fundamental drawback. In this review, we summarize the development of 3DED methods and their applications for structure elucidation of MOFs and COFs. Advances of 3DED data collection techniques are described, from step-wise rotation to continuous rotation of the crystal. The latter allows fast data collection which is crucial for beam sensitive materials including MOFs and COFs. Examples of ab initio structure determination of various MOFs and COFs by using 3DED are presented, with highlighted examples for solving the structures of mesoporous MOFs, mixed-metal MOFs, flexible MOFs, and for studying host-guest interactions. Finally, the accuracy and reproducibility of structure determination by 3DED are presented. We show the structure information obtained from 3DED provides crucial insights into structure-property relationships, which could further accelerate the development of new functional materials.

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A Robust and Biocompatible Bismuth Ellagate MOF Synthesized Under Green Ambient Conditions

2020. Erik Svensson Grape (et al.). Journal of the American Chemical Society 142 (39), 16795-16804

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The first bioinspired microporous metal-organic framework (MOF) synthesized using ellagic acid, a common natural antioxidant and polyphenol building unit, is presented. Bi2O(H2O)(2)(C14H2O8)center dot nH(2)O (SU-101) was inspired by bismuth phenolate metallodrugs, and could be synthesized entirely from nonhazardous or edible reagents under ambient aqueous conditions, enabling simple scale-up. Reagent-grade and affordable dietary supplement-grade ellagic acid was sourced from tree bark and pomegranate hulls, respectively. Biocompatibility and colloidal stability were confirmed by in vitro assays. The material exhibits remarkable chemical stability for a bioinspired MOF (pH = 2-14, hydrothermal conditions, heated organic solvents, biological media, SO2 and H2S), attributed to the strongly chelating phenolates. A total H2S uptake of 15.95 mmol g(-1) was recorded, representing one of the highest H2S capacities for a MOF, where polysulfides are formed inside the pores of the material. Phenolic phytochemicals remain largely unexplored as linkers for MOF synthesis, opening new avenues to design stable, eco-friendly, scalable, and low-cost MOFs for diverse applications, including drug delivery.

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A Tunable Multivariate Metal-Organic Framework as a Platform for Designing Photocatalysts

2021. Yang Wang (et al.). Journal of the American Chemical Society 143 (17), 6333-6338

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Catalysts for photochemical reactions underlie many foundations in our lives, from natural light harvesting to modern energy storage and conversion, including processes such as water photolysis by TiO₂. Recently, metal–organic frameworks (MOFs) have attracted large interest within the chemical research community, as their structural variety and tunability yield advantages in designing photocatalysts to address energy and environmental challenges. Here, we report a series of novel multivariate metal–organic frameworks (MTV-MOFs), denoted as MTV-MIL-100. They are constructed by linking aromatic carboxylates and AB₂OX₃ bimetallic clusters, which have ordered atomic arrangements. Synthesized through a solvent-assisted approach, these ordered and multivariate metal clusters offer an opportunity to enhance and fine-tune the electronic structures of the crystalline materials. Moreover, mass transport is improved by taking advantage of the high porosity of the MOF structure. Combining these key advantages, MTV-MIL-100(Ti,Co) exhibits a high photoactivity with a turnover frequency of 113.7 mol_H2 g_cat.^–1 min^–1, a quantum efficiency of 4.25%, and a space time yield of 4.96 × 10^–5 in the photocatalytic hydrolysis of ammonia borane. Bridging the fields of perovskites and MOFs, this work provides a novel platform for the design of highly active photocatalysts.

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Hexahydroxytriphenylene for the synthesis of group 13 MOFs - a new inorganic building unit in a beta-cristobalite type structure

2020. S. Leubner (et al.). Dalton Transactions 49 (10), 3088-3092

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Two new, microporous MOFs of framework composition ((CH3)(2)NH2)(2)[M3O(HHTP)(HHTP center dot)], M = Al3+, Ga3+, H6HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene, are described. Electron diffraction combined with molecular simulations show that these compounds crystallize in the beta-cristobalite structure, containing a new type of trinuclear inorganic building unit for MOFs and radical anions.

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An Expandable Hydrogen-Bonded Organic Framework Characterized by Three-Dimensional Electron Diffraction

2020. Peng Cui (et al.). Journal of the American Chemical Society 142 (29), 12743-12750

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A molecular crystal of a 2-D hydrogen-bonded organic framework (HOF) undergoes an unusual structural transformation after solvent removal from the crystal pores during activation. The conformationally flexible host molecule, ABTPA, adapts its molecular conformation during activation to initiate a framework expansion. The microcrystalline activated phase was characterized by three-dimensional electron diffraction (3D ED), which revealed that ABTPA uses out-of-plane anthracene units as adaptive structural anchors. These units change orientation to generate an expanded, lower density framework material in the activated structure. The porous HOF, ABTPA-2, has robust dynamic porosity (SA(BET) = 1 183 m(2) g(-1)) and exhibits negative area thermal expansion. We use crystal structure prediction (CSP) to understand the underlying energetics behind the structural transformation and discuss the challenges facing CSP for such flexible molecules.

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Highly Diastereoselective Palladium-Catalyzed Oxidative Cascade Carbonylative Carbocyclization of Enallenols

2020. Daniels Posevins (et al.). Organic Letters 22 (2), 417-421

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A palladium-catalyzed oxidative cascade carbonylative carbocyclization of enallenols was developed. Under mild reaction conditions, a range of cis-fused [5,5] bicyclic gamma-lactones and gamma-lactams with a 1,3-diene motif were obtained in good yields with high diastereoselectivity. The obtained lactone/lactam products are viable substrates for a stereoselective Diels-Alder reaction with N-phenylmaleimide, providing polycyclic compounds with increased molecular complexity.

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Breathing Metal-Organic Framework Based on Flexible Inorganic Building Units

2020. Erik Svensson Grape (et al.). Crystal Growth & Design 20 (1), 320-329

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Five novel bismuth carboxylate coordination polymers were synthesized from biphenyl-3,4',5-tricarboxylic acid (H3BPT) and [1,1':4',1 '']terphenyl-3,3 '',5,5 ''-tetracarboxylic acid (H4TPTC). One of the phases, [Bi(BPT)]center dot 2MeOH (denoted SU-100, as synthesized), is the first example, to the best of our knowledge, of a reversibly flexible bismuth-based metal-organic framework. The material exhibits continuous changes to its unit cell parameters and pore shape depending on the solvent it is immersed in and the dryness of the sample. Typically, in breathing carboxylate-based MOFs, flexibility occurs through tilting of the organic linkers without significantly altering the coordination environment around the cation. In contrast to this, the continuous breathing mechanism in SU-100 involves significant changes to bond angles within the Bi2O12 inorganic building unit (IBU). The flexibility of the IBU of SU-100 reflects the nondiscrete coordination geometry of the bismuth cation. A disproportionate increase in the solvent accessible void volume was observed when compared to the expansion of the unit cell volume of SU-100. Additionally, activated SU-100 (SU-100-HT) exhibits a large increase in unit cell volume, yet has the smallest void volume of all the studied samples.

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Permanent porosity and role of sulfonate groups in coordination networks constructed from a new polyfunctional phosphonato-sulfonate linker molecule

2020. Stephan Woehlbrandt (et al.). Dalton Transactions 49 (8), 2724-2733

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The new linker molecule (H2O3PCH2)(2)N-CH2C6H4SO3H, (4-{[bis(phosphonomethyl)amino]methyl}benzene-sulfonic acid, H5L), bearing both phosphonic and sulfonic acid groups, was employed for the synthesis of new coordination polymers (CPs). Four new CPs of composition [Mg(H3L)(H2O)(2)]H2O (1), [Mg-2(HL)(H2O)(6)]2H(2)O (2), [Ba(H3L)(H2O)]H2O (3) and [Pb-2(HL)]H2O (4), were discovered using high-throughput methods and all structures were determined by single-crystal X-ray diffraction (SCXRD). With increasing ionic radius of the metal ion, an increase in coordination number from CN = 6 (Mg2+) to CN = 9 (Ba2+) and an increase in the dimensionality of the network from 1D to 3D is observed. This is reflected in the composition of the IBU and the number of metal ions that are connected by each linker molecule, i.e. from three in 1 to ten in 4. The connection of the IBUs leads to 1D and 2D structures in 1 and 2 with non-coordinating sulfonate groups, while 3 and 4 crystallise in MOF-type structures and coordination of the sulfonate groups is observed. The compounds exhibit thermal stabilities between 200 (2) and 345 degrees C (4) as proven by variable temperature powder X-ray diffraction (VT-PXRD) measurements. Title compound 4 contains micropores of 4 x 2 angstrom and reversible H2O uptake of 50 mg g(-1) was demonstrated by vapour sorption measurements, making it the first porous metal phosphonatosulfonate. Detailed characterisation, i.e. CHNS and TG analysis as well as NMR and IR spectroscopy measurements confirm the phase purity of the title compounds.

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Silver-Triggered Activity of a Heterogeneous Palladium Catalyst in Oxidative Carbonylation Reactions

2020. Man-Bo Li (et al.). Angewandte Chemie International Edition

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A silver-triggered heterogeneous Pd-catalyzed oxidative carbonylation has been developed. This heterogeneous process exhibits high efficiency and good recyclability, and was utilized for the one-pot construction of polycyclic compounds with multiple chiral centers. AgOTf was used to remove chloride ions in the heterogeneous catalyst Pd-AmP-CNC, thereby generating highly active Pd-II, which results in high efficiency of the heterogeneous catalytic system.

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Water-based Synthesis and Properties of a Scandium 1,4-Naphthalenedicarboxylate

2020. Pia Rönfeldt (et al.). Zeitschrift für Anorganische und Allgemeines Chemie 646

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A new scandium naphthalenedicarboxylate with the framework composition [Sc-2(1,4-NDC)(3)] (H-2-1,4-NDC = 1,4-naphthalenedicarboxylic acid) was obtained under hydrothermal synthesis conditions. A structure model could be developed by a combination of 3D electron diffraction measurements and computationally assisted structure determination, which was further validated by a good agreement with the experimental powder X-ray diffraction pattern. The structure consists of isolated ScO6 octahedra interconnected by the carboxylate groups of linker molecules to form chains. These chains are connected by the naphthalene-moieties to form a three-dimensional framework with square-shaped pores and the organic group pointing into the pores. Although very similar synthesis conditions were chosen, [Sc-2(1,4-NDC)(3)] is not isostructural to aluminum naphthalenedicarboxylate [Al(OH)(1,4-NDC)], which crystallizes in a MIL-53 type structure. This can be traced back to the different inorganic building units that are observed. The compound was thoroughly characterized by elemental analysis, IR spectroscopy, sorption measurements, thermogravimetric analysis and luminescence measurements. [Sc-2(1,4-NDC)(3)] exhibits a high thermal stability and a ligand-based blue luminescence in the solid state at room temperature.

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Catalytic Enantioselective Synthesis of Bicyclic Lactam N,S-Acetals in One Pot by Cascade Transformations

2019. Kaiheng Zhang (et al.). European Journal of Organic Chemistry (29), 4649-4657

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A versatile strategy for the enantioselective synthesis of bicyclic lactam N,S-acetals by one-pot cascade transformations is disclosed. The transformation of readily available substrates is promoted by chiral amines and creates bicyclic or tricyclic lactam N,S-acetals with high chemo- and stereoselectivity (up to > 99.5:0.5 dr and > 99 % ee) in one-pot operations.

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A Tetratopic Phosphonic Acid for the Synthesis of Permanently Porous MOFs

2020. Stephan Wöhlbrandt (et al.). Inorganic Chemistry 59 (18), 13343-13352

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Following the strategy of installing porosity in coordination polymers predefined by linker geometry, we employed the new tetratopic linker molecule 1,1,2,2-tetrakis[4-phosphonophenyl]ethylene (H₈TPPE) for the synthesis of new porous metal phosphonates. A high-throughput study was carried out using Ni²⁺ and Co²⁺ as metal ions, and a very strong influence of the reactor size on the product formation is observed while maintaining the same reaction parameters. Using small autoclaves (V = 250 μL), single crystals of isostructural mononuclear complexes of the composition [Ni(H₃DPBP)₂(H₂O)₄] (1) and [Co(H₃DPBP)₂(H₂O)₄] (2) are formed. They contain the linker molecule H₄DPBP (4,4′-diphosphonobenzophenone), which is formed in situ by oxidation of H₈TPPE. Using autoclaves with a volume of V = 2 mL, two new 3D metal–organic frameworks (MOFs) of composition [Ni₂(H₄TPPE)(H₂O)₆]·4H₂O (CAU-46) and [Co₂(H₄TPPE)(H₂O)₄]·3H₂O (CAU-47) were isolated in bulk quantities, and their crystal structures were determined from three-dimensional electron diffraction (3D ED) and powder X-ray diffraction data. Using even larger autoclaves (V = 30 mL), another 3D MOF of the composition [Co₂(H₄TPPE)]·6H₂O (Co-CAU-48) was obtained, and a structure model was established via 3D ED measurements. Remarkably, the isostructural compound [Ni₂(H₄TPPE)]·9H₂O (Ni-CAU-48) is only obtained indirectly, i.e., via thermal activation of CAU-46. As the chosen linker geometry leads to the formation of MOFs, topological analyses were carried out, highlighting the different connectivities observed in the three frameworks. Porosity of the compounds was proven via water sorption experiments, resulting in uptakes of 126 mg/g (CAU-46), 105 mg/g (CAU-47), 210 mg/g (Ni-CAU-48), and 109 mg/g (Co-CAU-48).

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A metal-organic framework for efficient water-based ultra-low-temperature-driven cooling

2019. Dirk Lenzen (et al.). Nature Communications 10

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Efficient use of energy for cooling applications is a very important and challenging field in science. Ultra-low temperature actuated (T-driving< 80 degrees C) adsorption-driven chillers (ADCs) with water as the cooling agent are one environmentally benign option. The nanoscale metal-organic framework [Al(OH)(C6H2O4S)] denoted CAU-23 was discovered that possess favorable properties, including water adsorption capacity of 0.37 g(H2O)/g(sorbent) around p/p(0 )= 0.3 and cycling stability of at least 5000 cycles. Most importantly the material has a driving temperature down to 60 degrees C, which allows for the exploitation of yet mostly unused temperature sources and a more efficient use of energy. These exceptional properties are due to its unique crystal structure, which was unequivocally elucidated by single crystal electron diffraction. Monte Carlo simulations were performed to reveal the water adsorption mechanism at the atomic level. With its green synthesis, CAU-23 is an ideal material to realize ultra-low temperature driven ADC devices.

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Five New Coordination Polymers with a Bifunctional Phosphonate-Sulfonate Linker Molecule

2019. Stephan Wöhlbrandt (et al.). Zeitschrift für Anorganische und Allgemeines Chemie 645 (10), 732-739

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The bifunctional linker molecule [5-(phosphonomethyl)-2,4-bis(sulfonomethyl)phenyl]methanesulfonic acid (HO3S-CH2)(3)-C6H2-CH2PO3H2 (abbreviated as H(5)L4) was employed in systematic high-throughput investigations in order to discover new coordination polymers (CPs). Employing 27 metal salts of 17 different metals in this investigation, five new compounds [Mg-2(HL4)(H2O)(6)] (1), [Pb-4(L4)(OH)(3)] (2), [Ba-2(H(2)L4)(OH)(H2O)] (3), [Ba-2(HL4)(H2O)(4)] (4), and [Cd-2,Cd-5(L4)(H2O)(7)] (5) were discovered and their crystal structures were determined. In all compounds, the sulfonate and phosphonate groups could not be resolved since the P and S atoms are statistically occupying the atom site with a ratio of 0.25 to 0.75. This is reflected in the P-O and S-O bond lengths. Four of the structures were determined from single-crystal X-ray diffraction data, whereas the structure of 4 was solved ab initio from powder data using real-space methods and refined using Rietveld methods.

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Metal-Organic Frameworks as Catalysts for Organic Synthesis

2019. Vlad Pascanu (et al.). Journal of the American Chemical Society 141 (18), 7223-7234

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Recent advances in organic chemistry and materials chemistry have enabled the porosity of new materials to be accurately controlled on the nanometer scale. In this context, metal-organic frameworks (MOFs) have rapidly become one of the most attractive classes of solid supports currently under investigation in heterogeneous catalysis. Their unprecedented degree of tunability gives MOFs the chance to succeed where others have failed. The past decade has witnessed an exponential growth in the complexity of new structures. MOFs with a variety of topologies and pore sizes show excellent stability across wide ranges of pH and temperature. Even the controlled insertion of defects, to alter the MOF's properties in a predictable manner, has become commonplace. However, research on catalysis with MOFs has been sluggish in catching up with modern trends in organic chemistry. Relevant issues such as enantioselective processes, C-H activation, or olefin metathesis are still rarely discussed. In this Perspective, we highlight meritorious examples that tackle important issues from contemporary organic synthesis, and that provide a fair comparison with existing catalysts. Some of these MOF catalysts already outcompete state-of-the-art homogeneous solutions. For others, improvements may still be required, but they have merit in aiming for the bigger challenge. Furthermore, we also identify some important areas where MOFs are likely to make a difference, by addressing currently unmet needs in catalysis instead of trying to outcompete homogeneous catalysts in areas where they excel. Finally, we strongly advocate for rational design of MOF catalysts, founded on a deep mechanistic understanding of the events taking place inside the pore.

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In Situ XAS Study of the Local Structure and Oxidation State Evolutions of Palladium in a Reduced Graphene Oxide Supported Pd(II) Carbene Complex during an Undirected C−H Acetoxylation Reaction

2019. Ning Yuan (et al.). Catalysis Science & Technology 9 (8), 2025-2031

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In situ X-ray absorption spectroscopy (XAS) investigations have been performed to provide insights into the reaction mechanism of a palladium(II) catalyzed undirected C–H acetoxylation reaction in the presence of an oxidant. A Pd(II) N-heterocyclic carbene complex p-stacked onto reduced graphene oxide (rGO) was used as catalyst. The Pd speciation during the catalytic process was examined by XAS, which revealed a possible mechanism over the course of the reaction. Pd(II) complexes in the as-synthesized catalyst first go through a gradual ligand substitution where chloride ions bound to Pd(II) are replaced by other ligands with a bond distance to Pd corresponding to carbon, nitrogen and/or oxygen (L). Parallel to this the mean oxidation state of Pd increases indicating the formation of Pd(IV) species. At a later stage, a fraction of the Pd complexes start to slowly transform into Pd nanoclusters. The mean average oxidation state of Pd decreases to the initial state at the end of the experiment which means that comparable amounts of Pd(0) and Pd(IV) are present. These observations from heterogeneous catalysis are in good agreement with its homogeneous analog and they support a Pd(II)-Pd(IV)-Pd(II) reaction mechanism.

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Probing the active catalytic species generated from Pd(II)@MIL-101-NH2 in Heck coupling reactions: An operando X-ray absorption spectroscopy study

Ning Yuan (et al.).

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A Porous Cobalt Tetraphosphonate Metal-Organic Framework

2018. Bin Wang (et al.). Chemistry - A European Journal 24 (66), 17429-17433

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Single-crystal electron diffraction has shown to be powerful for structure determination of nano- and submicron-sized crystals that are too small to be studied by single-crystal X-ray diffraction. However, it has been very challenging to obtain high quality electron diffraction data from beam sensitive crystals such as metal-organic frameworks (MOFs). It is even more difficult to locate guest species in the pores of MOF crystals. Here, we present synthesis of a novel porous cobalt MOF with 1D channels, [Co-2(Ni-H4TPPP)]center dot 2DABCO center dot 6H(2)O, (denoted Co-CAU-36; DABCO=1,4-diazabicyclo[2.2.2]octane), and its structure determination using continuous rotation electron diffraction (cRED) data. By combining a fast hybrid electron detector with low sample temperature (96 K), high resolution (0.83-1.00 angstrom) cRED data could be obtained from eight Co-CAU-36 crystals. Independent structure determinations were conducted using each of the eight cRED datasets. We show that all atoms in the MOF framework could be located. More importantly, we demonstrate for the first time that organic molecules in the pores, which were previously difficult to find, could be located using the cRED data. A comparison of eight independent structure determinations using different datasets shows that structural models differ only on average by 0.03(2) angstrom for the framework atoms and 0.10(6) and 0.16(12) angstrom for DABCO and water molecules, respectively.

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Chemodivergent and Diastereoselective Synthesis of gamma-Lactones and gamma-Lactams

2018. Man-Bo Li (et al.). Journal of the American Chemical Society 140 (44), 14604-14608

Artikel

A palladium-catalyzed oxidative tandem process of enallenols was accomplished within a homogeneous/heterogeneous catalysis manifold, setting the stage for the highly chemodivergent and diaster-eoselective synthesis of gamma-lactones and gamma-lactams under mild conditions.

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Design and synthesis of dopant-free organic hole-transport materials for perovskite solar cells

2018. Linqin Wang (et al.). Chemical Communications 54 (69)

Artikel

Two novel dopant-free hole-transport materials (HTMs) with spiro[dibenzo[c,h]xanthene-7,9-fluorene] (SDBXF) skeletons were prepared via facile synthesis routes. A power conversion efficiency of 15.9% in perovskite solar cells is attained by using one HTM without dopants, which is much higher than undoped Spiro-OMeTAD-based devices (10.8%). The crystal structures of both new HTMs were systematically investigated to reveal the reasons behind such differences in performance and to indicate the design principles of more advanced HTMs.

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Lignin Based Molecular Materials - a Zinc Vanillate with a Hydrogen Bonded 4-and 8-connected Net with a New Topology

2018. Jurjen Spekreijse, Andrew Kentaro Inge, Lars Öhrström. Israel Journal of Chemistry 58 (9-10), 1127-1130

Artikel

Vanillic acid, C8H8O4, is a possible product from a future biorefinery with lignin as raw material. Two coordination compounds with this ligand in two different protonation states were prepared: 1 [Zn(C8H7O4)(2)(H2O)(2)] and 2 [Co-2(C8H6O4)(2)(H2O)(6)] 2H(2)O. Both compounds form extended 3D structures with strong hydrogen bonds. A high symmetry 8- and 4-connected network topology, jus, is found in 1. The dinuclear coordination entity in 2 hints at a potentially useful SBU for MOF synthesis from lignin based bridging ligands.

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Multistimuli-Responsive Enaminitrile Molecular Switches Displaying H+-Induced Aggregate Emission, Metal Ion-Induced Turn-On Fluorescence, and Organogelation Properties

2018. Yansong Ren (et al.). Journal of the American Chemical Society 140 (42), 13640-13643

Artikel

Multistimuli-responsive enaminitrile-based configurational switches displaying aggregation-induced emission (AIE), fluorescence turn-on effects, and super gelation properties are presented. The E-isomers dominated (>97%) in neutral/basic solution, and the structures underwent precisely controlled switching around the enamine C=C bond upon addition of acid/base. Specific fluorescence output was observed in response to different external input in the solution and solid states. In response to H+, configurational switching resulted in complete formation of the nonemissive Z-H+-isomers in solution, however displaying deep-blue to blue fluorescence (Phi(F) up to 0.41) in the solid state. In response to Cu-II in the solution state, the E-isomers exhibited intense, turn-on, blue-green fluorescence, which could be turned off by addition of competitive coordination. The acid/base-activated switching, together with the induced AIE-effects, further enabled the accomplishment of a responsive superorganogelator. In nonpolar solvents, a blue-fluorescent supramolecular gel was formed upon addition of acid to the E-isomer suspension. The gelation could be reversed by addition of base, and the overall, reversible process could be repeated at least five cycles.

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Probing the Evolution of Palladium Species in Pd@MOF Catalysts during the Heck Coupling Reaction: An Operando X-ray Absorption Spectroscopy Study

2018. Ning Yuan (et al.). Journal of the American Chemical Society 140 (26), 8206-8217

Artikel

The mechanism of the Heck C-C coupling reaction catalyzed by Pd@MOFs has been investigated using operando X-ray absorption spectroscopy (XAS) and powder X-ray diffraction (PXRD) combined with transmission electron microscopy (TEM) analysis and nuclear magnetic resonance (H-1 NMR) kinetic studies. A custom-made reaction cell was used, allowing operando PXRD and XAS data collection using high-energy synchrotron radiation. By analyzing the XAS data in combination with ex situ studies, the evolution of the palladium species is followed from the as-synthesized to its deactivated form. An adaptive reaction mechanism is proposed. Mononuclear Pd(II) complexes are found to be the dominant active species at the beginning of the reaction, which then gradually transform into Pd nanoclusters with 13-20 Pd atoms on average in later catalytic turnovers. Consumption of available reagent and substrate leads to coordination of Cl- ions to their surfaces, which causes the poisoning of the active sites. By understanding the deactivation process, it was possible to tune the reaction conditions and prolong the lifetime of the catalyst.

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Solvent-Dependent Formation of Three New Bi-Metal-Organic Frameworks Using a Tetracarboxylic Acid

2018. Milan Koeppen (et al.). Crystal Growth & Design 18 (7), 4060-4067

Artikel

Systematic solvent screening using high-throughput solvothermal syntheses with bismuth nitrate pentahydrate and 1,2,4,5-tetrakis-(4-carboxyphenyl)benzene (H4TCPB) led to three new porous Bi-metal-organic frameworks [Bi-2(H2TCPB)(TCPB)(H2O)(2)]center dot xH(2)O (CAU-31), (NH2(CH3)(2) [Bi(TCPB)(H2O)]center dot xH(2)O (CAU-32), and [Bi-4(O)(2)(OH)(2)(H2TCPB)(TCPB)(H2O)(2)]center dot xH(2)O (CAU-33). Compounds CAU-31, -32, and -33 were synthesized in CH3OH, CH3OH/DMF, and DMF/toluene, respectively. The crystal structures were determined using electron diffraction and single-crystal X-ray diffraction in combination with the Rietveld method. The structures of CAU-31 and CAU-32 are composed of isolated Bi3+ ions as the inorganic building unit (IBU), which are connected by the linker ions to form a layered structure with inclined interpenetration and a three-dimensional anionic network, respectively. The IBU of CAU-33 consists of infinite bismuth-oxo rods forming a three-dimensional network by connection of the organic linkers. For CAU-33 structural flexibility was observed, and two phases denoted alpha- and beta-CAU-33 could be isolated.

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Synthesis, Transformation, Catalysis, and Gas Sorption Investigations on the Bismuth Metal-Organic Framework CAU-17

2018. Milan Köppen (et al.). European Journal of Inorganic Chemistry (30), 3496-3503

Artikel

Very few microporous bismuth metal-organic frameworks have been discovered to date. Of these, no detailed experimental characterization of the synthesis and properties have been reported until now for the only one which can be prepared from inexpensive starting materials: CAU-17 [Bi(BTC)(H2O)], with H3BTC = trimesic acid. In-situ powder X-ray diffraction during solvothermal synthesis of CAU-17 revealed that it crystallizes rapidly within 2 minutes, and if the reaction is not stopped, the MOF transforms into a nonporous dense purely inorganic material within one hour, revealing that CAU-17 is a crystalline intermediate phase. Synthesis scale-up employing more concentrated reaction mixtures resulted in another Bi trimesate of composition [Bi(HBTC)(NO3)(MeOH)]MeOH, which structurally decomposes upon storage under ambient conditions. Sorption experiments showed that CAU-17 is microporous with a BET surface area of 530 m(2)/g. As a potential greenhouse gas sorbent, CAU-17 showed high SF6/N-2 and CO2/N-2 selectivity > 31 and 29, respectively. Furthermore, the catalytic activity of CAU-17 was studied in the regioselective ring-opening of styrene oxide by methanol to obtain 2-methoxy-2-phenylethanol, thus demonstrating the existence of coordinatively unsaturated sites in the crystal structure of CAU-17.

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Versatile Heterogeneous Palladium Catalysts for Diverse Carbonylation Reactions under Atmospheric Carbon Monoxide Pressure

2018. Marta Vico Solano (et al.). ChemCatChem 10 (5), 1089-1095

Artikel

Herein, we report a versatile carbonylation protocol using heterogeneous Pd-0 nanoparticles supported on the metal-organic frameworks (MOFs) MIL-88B-NH2 (Fe/Cr). The synthesis of a vast array of carbonyls, which includes amides, esters, carboxylic acids, and -ketoamides, was achieved through mono- and dicarbonylation reactions. The selectivity could be controlled simply by tuning the reaction conditions. Superior activity and selectivity were recorded in some cases compared to that achieved with commercial Pd/C. However, the utility of an elaborate catalyst support is questionable and important reactivity and recyclability issues are discussed.

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Elucidation of the elusive structure and formula of the active pharmaceutical ingredient bismuth subgallate by continuous rotation electron diffraction

2017. Yunchen Wang (et al.). Chemical Communications 53 (52), 7018-7021

Artikel

Bismuth subgallate has been used in wound and gastrointestinal therapy for over a century. The combination of continuous rotation electron diffraction and sample cooling finally revealed its structure as a coordination polymer. The structure provides insight regarding its formula, poor solubility, acid resistance and previously unreported gas sorption properties.

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A Water Based Synthesis of Ultrathin Hydrated Vanadium Pentoxide Nanosheets for Lithium Battery Application

2017. Ahmed S. Etman (et al.). Electrochimica Acta 252, 254-260

Artikel

Ultrathin hydrated vanadium pentoxide (V2O5 center dot nH(2)O) nanosheets are fabricated via a water based exfoliation technique. The exfoliation process involves reflux of the precursor, 1:4 mixture of VO2 and V2O5, in water at 80 degrees C for 24 h. Operando and ex situ X-ray diffraction (XRD) studies are conducted to follow the structural changes during the exfoliation process. The chemical and thermal analyses suggest that the molecular formula of the nanosheet is (H0.2V1.8V0.2O5)-V-V-O-IV center dot 0.5H(2)O. The V2O5 center dot nH(2)O nanosheets are mixed with 10% of multi-walled carbon nanotube (MW-CNT) to form a composite material assigned as (VOx-CNT). Free standing electrodes (FSE) and conventionally casted electrodes (CCE) of VOx-CNT are fabricated and then tested as a positive electrode material for lithium batteries. The FSE shows reversible capacities of 300 and 97 mAhg(-1) at current densities of 10 and 200 mAhg(-1), respectively. This is better than earlier reports for free-standing electrodes. The CCE delivers discharge capacities of 175 and 93 mAhg(-1) at current densities of 10 and 200 mAhg(-1), respectively.

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A multi-purpose reaction cell for the investigation of reactions under solvothermal conditions

2017. N. Heidenreich (et al.). Review of Scientific Instruments 88 (10)

Artikel

A new versatile and easy-to-use remote-controlled reactor setup aimed at the analysis of chemical reactions under solvothermal conditions has been constructed. The reactor includes a heating system that can precisely control the temperature inside the reaction vessels in a range between ambient temperature and 180 degrees C. As reaction vessels, two sizes of commercially available borosilicate vessels (V-max = 5 and 11 ml) can be used. The setup furthermore includes the option of stirring and injecting of up to two liquid additives or one solid during the reaction to initiate very fast reactions, quench reactions, or alter chemical parameters. In addition to a detailed description of the general setup and its functionality, three examples of studies conducted using this setup are presented.

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Effect of partial linker fluorination and linker extension on structure and properties of the Al-MOF CAU-10

2017. Martin Krüger (et al.). Microporous and Mesoporous Materials 249, 128-136

Artikel

The systematic investigation of the solvothermal system Al3+/5-fluoroisophthalic acid (H(2)mBDC-5F)/isophthalic acid (H(2)mBDC)/DMF/H2O through a mixed-linker approach led to new mixed-linker CAU-10 derivatives containing 11, 28 and 44% of fluorinated linker molecules (denoted as CAU-10-H/F-11, CAU-10-H/F-28 and CAU-10-H/F-44, respectively), as determined by NMR spectroscopy. The crystal structure of CAU-10-H/F-28 was determined using the Rietveld method (space group 14(1)md, a = b = 21.3075(5), c = 10.7101(3) angstrom). The structure is built up by helical chains composed of cis corner-sharing AlO6 polyhedra. Each of these helices is interconnected to four adjacent helices with alternating rotational orientation through the carboxylate groups of mBDC(2-) linker molecules. Thus, accessible, square-shaped channels are formed. Sorption measurements revealed a high dependency of the adsorbed amount of gas on the degree of fluorination. With increasing fluorination, the total uptake decreases in N-2, H-2 and H2O sorption experiments and the hydrophobic character of the pores increases. In addition, an extended CAU-10 derivative, CAU-10-HTATB, was discovered using the tricarboxylic acid 4,4',4-s-triazine-2,4,6-triyl-tribenzoic acid (H(3)TATB) during the high-throughput investigation of the system Al3+/H(3)TATB/DMF/H2O. This new MOF, which was denoted CAU-10-HTATB, was thoroughly characterized using IR spectroscopy, thermogravimetric and elemental analysis, temperature dependent powder X-ray diffraction (PXRD) and sorption measurements. Although the compound is thermally stable up to 400 degrees C according to temperature-dependent PXRD measurements, it is not porous towards N2 molecules. The structure of CAU-10-HTATB could be also refined from PXRD data using the Rietveld method (space group l4(1)/a, a = b = 36.438 (1), c = 10.9373 (9) angstrom).

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Investigation of the effect of polar functional groups on the crystal structures of indium MOFs

2017. Martin Krüger (et al.). CrystEngComm 19 (31), 4622-4628

Artikel

Three new In-MOFs with -NH2 and/or -NO2 functionalities are reported using 2-amino-(H2BDC-NH2), 2-nitro-(H2BDC-NO2) and 2-amino-5-nitroterephthalic acid (H2BDC-NH2/NO2). Their structures were determined from single crystal X-ray diffraction data. The structure of the first In-MOF of composition [In(BDC-NH3)(BDC-NH2)] center dot 1.6DMF center dot 1.9H(2)O (In-BDC-NH2;DMF is dimethylformamide; the space group is P6(2)22, a = b = 14.738(2) angstrom and c = 12.257(3) angstrom) is built up by two interpenetrating nets of InOB polyhedra interconnected by BDC-NH2 2-ions to form a framework with qtz topology. Charge balance is accomplished by partial protonation of the amino group, which was confirmed by IR spectroscopy. The interpenetration leads to a decrease of the pore dimension (4.4 angstrom in diameter). Thermogravimetric analysis revealed stability up to 300 degrees C. Replacement of H2BDC-NH2 by H2BDC-NO2 in the reaction mixture led to the iso-reticular MOF containing no -NO2 groups but exclusively un- and amino-functionalized linkers. Hence an indium mediated reduction of the H2BDC-NO2 linker molecule during solvothermal synthesis has occurred. The use of H2BDC-NH2/NO2 under exactly the same reaction conditions did not result in the formation of a MOF, but by changing the synthesis parameters, a new -NH2/-NO2 bifunctionalised In-MOF of composition (DMA)(2).In-3.mu(3)-O)(BDC-NH2/NO2) 4.5] center dot DMF (DMA is dimethylammonium), denoted In-BDC-NH2/NO2, was obtained. The crystal morphology can be altered from cubic to truncated octahedral crystals by varying the DMF/ethanol volume ratio during synthesis. The compound crystallises in the cubic space group I43m, a = 24.8947(1) angstrom, and the framework contains trinuclear {In-3.mu(3)-O)} clusters which are interlinked by the BDC-NH2/NO2 2-ions to form super-tetrahedra. Four face-sharing super-tetrahedra form ultra-tetrahedra which are connected to form the final cubic framework with an ncb topology and isolated inaccessible pores.

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Polymorphous Al-MOFs Based on V-Shaped Linker Molecules

2017. Martin Krüger (et al.). Inorganic Chemistry 56 (10), 5851-5862

Artikel

The in situ and systematic high-throughput investigation of the system Al3+/4,4'-benzophenonedicarboxylic acid (H2BPDC)/DMF/H2O in the presence of various additives was carried out, and a new Al-MOF of composition [Al(OH)(BPDC)], denoted as CAU-21-BPDC, was obtained. Its crystal structure was determined from single-crystal X-ray diffraction data (space group I422, a = b = 17.2528(7) angstrom, c = 23.864(1) angstrom). The structure is built up by octanuclear rings of cis corner-sharing AlO6 polyhedra forming the inorganic building unit (IBU). These {Al8O8} IBUs are arranged in a bcu packing and connected via BPDC2(-) ions in a way that each IBU is linked via two linker molecules to each of the eight adjacent IBUs. Thus, accessible, one-dimensional modulated pores with a diameter between 3.6 and 6.5 angstrom are formed. In addition, tetrahedral cavities are formed by the BPDC2(-) linker molecules. The framework of CAU-21-BPDC is polymorphous with that of CAU-8-BPDC, which contains one-dimensional chains of trans corner-sharing AlO6 polyhedra connected by BPDC2(-) ions. Replacing H2BPDC by 4,4'-oxydibenzoic acid (H2ODB), which contains an oxygen atom between the phenyl rings instead of a keto group, leads to the synthesis of Al-MOFs isoreticular with CAU-8-BPDC and CAU-21-BPDC. In addition, a coordination polymer, [Al(HODB)2(OH)], was discovered and structurally characterized. The structure of CAU-8-ODB was refined from powder X-ray diffraction data, while a Pawley refinement was carried out for CAU-21-ODB to determine the lattice parameters and confirm phase purity. The structure of CAU-21-ODB was confirmed using density functional theory (DFT) calculations. A thorough characterization shows that the CAU-8 and CAU-21-type structures are stable up to 350 and 300 degrees C in air, respectively, almost independent of the linker molecules incorporated. The former MOFs are porous toward N-2 and CO2, while the latter only adsorb CO2.

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Synthesis and crystal structure of three new bismuth(III) arylsulfonatocarboxylates

2017. Martin Albat, Andrew Kentaro Inge, Norbert Stock. Zeitschrift für Kristallographie - Crystalline Materials 232 (1-3), 245-253

Artikel

Three new bismuth arylsulfonatocarboxylates [Bi(OH)(SB)] (1), [Bi-4(ST)(2)(HST)O-2(H2O)(2)]center dot H2O (2) and [Bi-4(ST)(2)O-3(H2O)(2)] (3) were synthesized under solvothermal reaction conditions at 180 degrees C using the potassium or sodium salt of 4-sulfobenzoic acid (H2SB) and 2-sulfoterephthalic acid (H3ST), respectively. The compounds were characterized in detail and the crystal structures were determined from single crystal X-ray diffraction data. Phase purity was confirmed by powder X-ray diffraction and elemental analysis. Structural comparisons to the only three other known bismuth sulfonatocarboxylates are presented. Due to the higher reaction temperatures employed for the synthesis of the title compounds a higher degree of condensation of the BiOx polyhedra (X = 7 or 8) to tetrameric units, 1D chains or a 2D layer is observed. Connection through the organic linker molecules leads to the formation of 3D coordination polymers in all three title compounds.

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Unprecedented Topological Complexity in a Metal-Organic Framework Constructed from Simple Building Units

2016. Andrew Kentaro Inge (et al.). Journal of the American Chemical Society 138 (6), 1970-1976

Artikel

A bismuth-based metal-organic framework (MOP), [Bi(BTC)(H2O)]center dot 2H(2)O center dot MeOH denoted CAU-17, was synthesized and found to have an exceptionally complicated structure with helical Bi-O rods cross-linked by 1,3,5-benzenetricarboxylate (BTC3-) ligands. Five crystallographically independent 1D channels including two hexagonal channels, two rectangular channels, and one triangular channel have accessible diameters of 9.6, 9.6, 3.6, 3.6, and 3.4 angstrom, respectively. The structure is further complicated by twinning. Rod-incorporated MOF structures typically have underlying nets with only one unique node and three or four unique edges. In contrast, topological analysis of CAU-17 revealed unprecedented complexity for a MOF structure with 54 unique nodes and 135 edges. The complexity originates from the rod packing and the rods themselves, which are related to aperiodic helices.

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A Germanate with a Collapsible Open-Framework

2016. A. Ken Inge (et al.). Crystal Growth & Design 16 (12), 6967-6973

Artikel

A novel open-framework germanate, vertical bar NC2H8 vertical bar vertical bar N2C6H18 vertical bar, [Ge7O14.5F2].4H(2)O denoted SU-65 (SU = Stockholm University), with 24-ring channels and a very low framework density of 8.9 Ge atoms per 1000 angstrom(3) was synthesized under hydro-solvothermal conditions. The framework of SU-65 is built of 5-connected Ge-7 clusters decorating the fee net and is a framework orientation isomer to ASU-16. Half of the 8- and 12-rings in ASU-16 are instead 10-rings in SU-65 due to the different orientations of half of the clusters in the crystal structure. Flexibility of the frameworks is also influenced by the orientation of the clusters. The unique unit cell angle in SU-65 changes upon heating, unlike ASU-16 which only undergoes changes in unit cell lengths. SU-65 undergoes significant structural changes at 180 degrees C in a vacuum, forming SU-65ht. The crystal structure of SU-65ht was investigated by rotation electron diffraction, X-ray powder diffraction, and infrared spectroscopy. Through these techniques it was deduced that SU-65ht has similar clusters, symmetry, and topology as SU-65, but one of the unit cell lengths is shortened by approximately 5 A. This corresponds to a 22% decrease in unit cell volume.

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Dihydroxybenzoquinone as Linker for the Synthesis of Permanently Porous Aluminum Metal-Organic Frameworks

2016. Seida Halis (et al.). Inorganic Chemistry 55 (15), 7425-7431

Artikel

Two new dihydroxybenzoquinone-based metal-organic frameworks, ((CH3)(2)NH2)(3)[Al-4(L1)(3)(L1(center dot))(3)]center dot 3DMF (1, denoted CAU - 20) and ((CH3)(2)NH2)(3)[Al-4(L2)(3)(L2 center dot)(3)]center dot 9DMF (2, denoted CAU-20-Cl-2), were synthesized at 120 degrees C in PAU using 2,5-dihydroxy-p-benzoquinone ((C6H2(OH)(2)(O)(2)), H(2)L1) and 2,5-dichloro-3,6-dihydroxy-p-benzoquinone ((C6Cl2(OH)(2)(O)(2)), H(2)L2), respectively. Compared to other Al-MOFs, which contain carboxylate or phosphonate groups that connect the metal sites, in 1 and 2 the Al3+ are coordinated by oxido groups. The metal ions are octahedrally surrounded by oxygen atoms Of the deprotonated linker molecules to generate honeycomb layers with a metal to linker ratio of Al: L1/L2 = 2:3. The layers contain L1(2-) and L2(2-) ions as well as linker radical ions L1(center dot 3-) and L2(center dot 3-) in a molar ratio of 1 to 1. The presence of radical ions was confirmed by EPR and UV-vis-spectroscopic Measurements, and the composition was determined from a combination of PXRD, H-1, NMR, TG, and elemental analyses. Charge balance is accomplished through intercalation of (CH3)(2)NH2+ ions which are formed by partial hydrolysis of DMF. In the structures of 1 and 2 the eclipsed layers are AA and ABAB stacked, respectively, and one-dimensional hexagonal channels with diameters of ca. 9 and 6 angstrom are formed. Both compounds exhibit permanent porosity and have specific surface areas of 1440 and 1430 m(2) g(-1), respectively.

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Solving complex open-framework structures from X-ray powder diffraction by direct-space methods using composite building units

2013. A. Ken Inge (et al.). Journal of applied crystallography 46, 1094-1104

Artikel

The crystal structure of a novel open-framework gallogermanate, SU-66 {|(C6H18N2)(18)(H2O)(32)|[Ga4.8Ge87.2O208]}, has been solved from laboratory X-ray powder diffraction (XPD) data by using a direct-space structure solution algorithm and local structural information obtained from infrared (IR) spectroscopy. IR studies on 18 known germanates revealed that the bands in their IR spectra were characteristic of the different composite building units (CBUs) present in the structures. By comparing the bands corresponding to Ge-O vibrations in the IR spectra of SU-66 with those of the 18 known structures with different CBUs, the CBU of SU-66 could be identified empirically as the Ge-10(O,OH)(27) cluster (Ge-10). The unit cell and space group (extinction symbol P--a; a = 14.963, b = 31.593, c = 18.759 angstrom) were determined initially from the XPD pattern and then confirmed by selected-area electron diffraction. The structure of SU-66 was solved from the XPD data using parallel tempering as implemented in FOX [Favre-Nicolin & Cerny (2002). J. Appl. Cryst. 35, 734-743] by assuming P2(1)ma symmetry and two Ge-10 clusters in the asymmetric unit. Rietveld refinement of the resulting structure using synchrotron XPD data showed the framework structure to be correct and the space group to be Pmma. The framework has extra-large (26-ring) onedimensional channels and a very low framework density of 10.1 Ge/Ga atoms per 1000 angstrom(3). SU-66, with 55 framework atoms in the asymmetric unit, is one of the more complicated framework structures solved from XPD data. Indeed, 98% of the reflections were overlapping in the XPD pattern used for structure solution. Tests on other open-framework germanates (SU-62, SU-65, SU-74, PKU-12 and ITQ-37) for which the XPD data, unit cell, space group and IR spectra were available proved to be equally successful. In a more complex case (SU-72) the combination of FOX and powder charge flipping was required for structure solution.

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Catalytic Water Oxidation by Mononuclear Ru Complexes with an Anionic Ancillary Ligand

2013. Lianpeng Tong (et al.). Inorganic Chemistry 52 (5), 2505-2518

Artikel

Mononuclear Ru-based water oxidation catalysts containing anionic ancillary ligands have shown promising catalytic efficiency and intriguing properties. However, their insolubility in water restricts a detailed mechanism investigation. In order to overcome this disadvantage, complexes [Ru-II(bpc)(bpy)OH2](+) (1(+), bpc = 2,2'-bipyridine-6-carboxylate, bpy = 2,2'-bipyridine) and [Ru-II(bpc)(pic)(3)](+) (2(+), pic = 4-picoline) were prepared and fully characterized, which features an anionic tridentate ligand and has enough solubility for spectroscopic study in water. Using Ce-IV as an electron acceptor, both complexes are able to catalyze O-2-evolving reaction with an impressive rate constant. On the basis of the electrochemical and kinetic studies, a water nucleophilic attack pathway was proposed as the dominant catalytic cycle of the catalytic water oxidation by 1(+), within which several intermediates were detected by MS. Meanwhile, an auxiliary pathway that is related to the concentration of Ce-IV was also revealed. The effect of anionic ligand regarding catalytic water oxidation was discussed explicitly in comparison with previously reported mononuclear Ru catalysts carrying neutral tridentate ligands, for example, 2,2':6',2 ''-terpyridine (tpy). When 2(+) was oxidized to the trivalent state, one of its picoline ligands dissociated from the Ru center. The rate constant of picoline dissociation was evaluated from time-resolved UV-vis spectra.

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Open-Framework Germanates and Related Materials

2013. Andrew Kentaro Inge, Xiaodong Zou. Nanoporous Materials

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A Highly Active Bifunctional Iridium Complex with an Alcohol/Alkoxide-Tethered N-Heterocyclic Carbene for Alkylation of Amines with Alcohols

2012. Agnieszka Bartoszewicz (et al.). Chemistry - A European Journal 18 (45), 14510-14519

Artikel

A series of new iridium(III) complexes containing bidentate N-heterocyclic carbenes (NHC) functionalized with an alcohol or ether group (NHC?OR, R=H, Me) were prepared. The complexes catalyzed the alkylation of anilines with alcohols as latent electrophiles. In particular, biscationic IrIII complexes of the type [Cp*(NHC-OH)Ir(MeCN)]2+2[BF4-] afforded higher-order amine products with very high efficiency; up to >99?% yield using a 1:1 ratio of reactants and 12.5 mol?% of Ir, in short reaction times (216 h) and under base-free conditions. Quantitative yields were also obtained at 50?degrees C, although longer reaction times (4860 h) were needed. A large variety of aromatic amines have been alkylated with primary and secondary alcohols. The reactivity of structurally related iridium(III) complexes was also compared to obtain insights into the mechanism and into the structure of possible catalytic intermediates. The IrIII complexes were stable towards oxygen and moisture, and were characterized by NMR, HRMS, single-crystal X-ray diffraction, and elemental analyses.

Läs mer om A Highly Active Bifunctional Iridium Complex with an Alcohol/Alkoxide-Tethered N-Heterocyclic Carbene for Alkylation of Amines with Alcohols

A Stacking Faults-Containing Silicogermanate with 24-Ring Channels and Unbranched Zweier Silica Double Chains

2012. Liqiu Tang (et al.). Crystal Growth & Design 12 (7), 3714-3719

Artikel

A novel open-framework silicogermanate SU-JU-14 (Stockholm University-Jilin University-Number 14), vertical bar NH3CH2CH2NH3 vertical bar(3)[Ge6.40Si0.60O15(OH)](2)[Ge0.73Si3.27O8], was synthesized by using ethylenediamine as the structure-directing agent under solvothermal conditions. Single-crystal structure analysis reveals that the crystal structure of SU-JU-14 consists of extended 24-ring channels built from [(Ge,Si)(7)O12O6/2(OH)](3-) [(Ge,Si)(7)] clusters and unbranched zweier silica double chains [Ge0.73Si3.27O4O8/2]. Charge neutrality is achieved by diprotonated ethylenediamine guest molecules. The structure consists of stacking faults of layered arrays in two different configurations along the a-axis. SU-JU-14 was characterized by X-ray diffraction, X-ray energy dispersive spectroscopy, scanning electron microscopy, nuclear magnetic resonance, inductively coupled plasma, and thermogravimetric analyses. Crystallographic data: monoclinic, space group C2/c, and unit cell parameters: a = 35.625 (7) angstrom, b = 28.580 (6) angstrom, c = 10.403 (2) angstrom, and beta = 98.30 (3)degrees.

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Three Low-Dimensional Open-Germanates Derived from the 4^4 Net

Andrew Kentaro Inge (et al.). CrystEngComm

Artikel

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Open-Framework Germanates

2012. Andrew Kentaro Inge, Xiaodong Zou, Anthony Cheetham.

Avhandling (Dok)

Novel open-framework germanates and open low-dimensional structures were synthesized and characterized. Their crystal structures were solved by single crystal X-ray diffraction or X-ray powder diffraction combined with other techniques. Although related open-framework materials, such as zeolites, are of interest for the ability to selectively accommodate guest species in their rings, pores and channels, germanates are primarily of interest for their unique structural properties. Compared to aluminosilicate-based zeolites, germanium oxides readily form frameworks with extra-large rings and low framework density. The formation of elegant germanate architectures is attributed to the unique Ge-O bond geometries compared to Si-O, and the tendency to form large clusters.

This thesis is to serve as an introduction to germanate synthesis, structures and characterization. Structures are categorized in accordance to their building units; the Ge₇X₁₉ (Ge₇), Ge₉X_25-26 (Ge₉) and Ge₁₀X₂₈ (Ge₁₀) (X = O, OH, or F) clusters. Structure determination techniques as well as the characterization techniques used to examine the properties of the materials are presented. While most of the discussed techniques have routinely been used to study crystalline open-frameworks, we introduce the use of infrared spectroscopy for the identification of cluster types, valuable for structure determination by X-ray powder diffraction. Structures and properties of the novel materials ASU-21, SU-62, SU-63, SU-64, SU-65, SU-66, SU-71, SU-72, SU-73, SU-74, SU-75 and SU-JU-14 are described and put into context with previously known structures. The novel structures are all built of the Ge₇, Ge₉ or Ge₁₀ clusters, and vary from a framework with novel topology to the first open zero-dimensional germanate cavities built of such clusters.

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SU-62

2012. Andrew Kentaro Inge (et al.). Crystal Growth & Design 12 (1), 369-375

Artikel

A novel 3D open-framework germanate, vertical bar N(2)C(4)H(14)vertical bar(4) [Ge(20)O(41)(OH)(6)]center dot 3H(2)O (SU-62), was prepared from hydrothermal synthesis using 1,4-diaminobutane as the organic structure directing agent (SDA). The crystal structure was solved by single crystal X-ray diffraction. The framework is built from Ge(10)(O,OH)(27) (Ge(10)) secondary building units and exhibits an irregular three-dimensional channel system encircled by 10- and 14-rings. The framework of SU-62 has an underlying topology that follows a novel five-coordinated svh-5-I4(1)/amd net, while the pores follow the tsi net. The thermal behavior of SU-62 was studied by thermogravimetric (TG) analysis and in situ X-ray diffraction (XRPD). Crystallographic data: orthorhombic, space group Fdd2, unit cell parameters a = 15.297(3) angstrom, b = 53.58(1) angstrom, c = 14.422(3) angstrom, V = 11821(4) angstrom(3), Z = 8.

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SU-75

2012. Shiliang Huang (et al.). Dalton Transactions 41 (40), 12358-12364

Artikel

A disordered open-framework germanate, denoted as SU-75, was synthesized under hydrothermal conditions using diethylenetriamine (dien) or alternatively 1,4-diaminobutane (dab) as the structure directing agent (SDA). SU-75 crystallizes in a tetragonal space group I-42d(No. 122) with a= 18.145(3) Å and c= 41.701(9) Å. The three-dimensional (3D) framework is built from Ge10(O,OH)28(Ge10) clusters that are connected following the pcu ( primitive cubic) net topology. SU-75 has 10-, 11- and 12-ring channels along the a- and b-axes and channels with alternating 8-, 10-, 12-, 10-ring openings along the c-axis. The framework exhibits a serious disorder, resulted from two possible connectivities between the units of four Ge 10clusters (4Ge10 unit). The chemical formula of SU-75 is |(H2SDA)2(H2O)n|[Ge10O21(OH)2] (SDA = dien or dab,n= 5–6), determined by combining single crystalsynchrotron X-ray diffraction, thermogravimetric analysis (TGA) and CHN elemental analysis. A superoctahedron is introduced to simplify the description of the connectivity of the Ge10 clusters and to illustrate the disorder. This is also used to compare the structure of SU-75 with those of related Ge10 germanates.

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SU-65

Andrew Kentaro Inge (et al.).

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The Structure of a Complex Open-framework Germanate Obtained by Combining Powder Charge-Flipping and Simulated Annealing

2012. Andrew Kentaro Inge (et al.). Crystal Growth & Design 12 (10), 4853-4860

Artikel

A novel open-framework germanate SU-74 containing intersecting 10- and 12-ring channels was prepared by hydrothermal synthesis using 2-methylpentamethylenediamine (MPMD) or 1-(2-aminoethyl)piperazine (AEP) as the organic structure directing agent (SDA). The framework structure of SU-74-MPMD was solved from X-ray powder diffraction (XRPD) data using powder charge-flipping (pCF). The guest species H2MPMD2+, NH4+ cations and water molecules were located in the voids using real-space simulated annealing. SU-74-MPMD contains 51 non-hydrogen atoms in its asymmetric unit and is one of the most complex framework structures solved by XRPD. The structure of SU-74-AEP was solved by single crystal synchrotron X-ray diffraction. SU-74-MPMD and SU-74-AEP have the same framework structure. The location of the NH4+ cations in both structures is similar, while the positions of the SDAs in the pores are different. SU-74 follows the fcu-11-P21/c net. The underlying topology of SU-74 is compared to those of other Ge10 structures containing additional GeO4 tetrahedra. The presence of additional tetrahedra can significantly affect the framework topology through the addition of edges between the Ge10 nodes.

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Investigation of the GeO₂-1,6-Diaminohexane-Water-Pyridine-HF Phase Diagram Leading to the Discovery of Two Novel Layered Germanates with Extra-Large Rings

2011. Bing Guo (et al.). Inorganic Chemistry 50 (1), 201-207

Artikel

The systematic exploration of the phase diagram of the GeO₂-1,6-diaminohexane-water-pyridine-HF system has allowed the identification of specific roles of the HF, H₂O contents, and HF/H₂O ratio in the formation of Ge₇X₁₉ (Ge₇), Ge₉X₂₅₋₂₆ (Ge₉), and Ge₁₀X₂₈ (Ge₁₀) clusters (X = O, OH, F). This work has led to the discovery of two novel structures with extra-large 18-membered rings accommodating 1,6-diaminohexane (DAH): SU-63, |1.5H₂DAH|[Ge₇O₁₄X₃]·2H₂O, a layered germanate constructed from Ge₇ clusters with the Kagom topology, and SU-64, |11H₂DAH|[Ge₉O₁₈X₄][Ge₇O₁₄X₃]₆·16H₂O, a germanate built of two-dimensional slabs containing both Ge₇ and Ge₉ clusters (X = OH or F). We also put SU-64 in context with previously reported cluster germanate compounds with related topologies by means of a simple crystal deconstruction study.

Läs mer om Investigation of the GeO₂-1,6-Diaminohexane-Water-Pyridine-HF Phase Diagram Leading to the Discovery of Two Novel Layered Germanates with Extra-Large Rings

Synthesis and characterization of oligonuclear Ru, Co, and Cu oxidation catalysts

2010. Bao-Lin Lee (et al.). European Journal of Inorganic Chemistry (34), 5462-5470

Artikel

In this work, we report the preparation and crystal structures of three new oligonuclear complexes, Ru-2(bbpmp)(mu-OAc)(3) (4), [Co-2(bbpmp)(mu-OAc)(mu-OMe)](PF6) (5), [Cu-4(Hbbpmp)(2)(mu-OAc)(H2O)(2)](OAc)(PF6)(2) (6) {H(3)bbpmp = 2,6-bis[(2-hydroxybenzyl)-(2-pyridylmethyl)aminomethyl]-4-methylphenol (3)}. The structures of the complexes were determined by single-crystal X-ray diffraction. The oxidation states of ruthenium, cobalt and copper in the complexes are +3, +3 and +2, respectively. In 4 and 5, Ru-III and Co-III are coordinated to four oxygen and two nitrogen atoms in an octahedral geometry, while in 6, Cu-II adopts both octahedral (CuN2O4) and square-pyramidal (CuN2O3) geometry. The potential of the three complexes as oxidation catalysts has been investigated.

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Open-Framework Germanate Built from the Hexagonal Packing of Rigid Cylinders

2009. Charlotte Bonneau (et al.). Inorganic Chemistry 48 (21), 9962-9964

Artikel

We present a novel open-framework oxide material constructed from Ge₁₀(O,OH)₂₈ (Ge₁₀) oxide clusters prepared via a nonsurfactant route. The material shows two distinct pore windows of 9.43 and 4.65 Å and a low framework density structure of 12.7 Ge atoms per 1000 Å³. The topological study leads to the recognition of a newly observed trinodal 6,7-heterocoordinated net related to the 7-coordinated swh net. The structure displays large rigid cylinders showing features indicating a growth mechanism by hard-sphere packing of the inorganic moiety similar to that observed in mesoporous materials.

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Promoting the Fe(VI) active species generation by structural and electronic modulation of efficient iron oxide based water oxidation catalyst without Ni or Co

2020. Lizhou Fan (et al.). Nano Energy 72

Artikel

Fe is considered as a promising alternative for OER catalysts owing to its high natural abundance and low cost. Due to the low conductivity and sluggish catalytic kinetics, the catalytic efficiency of Fe-rich catalysts is far from less abundant Ni, Co-rich alternatives and has been hardly improved without the involvement of Ni or Co. The lower activity of Fe-rich catalysts renders the real active center of state-of-the-art NiFe, CoFe catalyst in long-term scientific debate, despite of detection of Fe-based active intermediates in these catalysts during catalytic process. In the present work, we fabricated a series of sub-5 nm Fe1-yCryOx nanocatalysts via a simple solvothermal method, achieving systematically promoted high-valent Fe(VI) species generation by structural and electronic modulation, displaying highly active OER performance without involvement of Ni or Co. Detailed investigation revealed that the high OER activity is related to the ultrasmall nanoparticle size that promotes abundant edge- and corner-site exposure at catalyst surface, which involves in OER as highly reactive site; and the incorporated Cr ions that remarkably accelerate the charge transfer kinetics, providing an effective conduit as well as suitable host for high-valent active intermediate. This work reveals the structural prerequisites for efficient Fe-rich OER catalyst fabrication, inspiring deeper understanding of the structure-activity relationship as well as OER mechanism of Fe-based catalysts.

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Amorphous WO3 induced lattice distortion for a low-cost and high-efficient electrocatalyst for overall water splitting in acid

2020. Ke Fan (et al.). Sustainable Energy & Fuels 4 (4), 1712-1722

Artikel

The development of highly active and durable catalysts for water oxidation under acidic conditions is necessary but challenging for renewable energy conversion. Ir-based catalysts are highly efficient for water oxidation in acid, but their large scale application is hindered by the high cost and scarcity of iridium. Herein, we use an amorphous WO3 induced lattice distortion (AWILD) strategy to reduce the Ir content to only 2 wt% in the final material. The optimized hybrid nitrogen-doped carbon (NC)/WO3/IrO2 can efficiently catalyze water oxidation with a low overpotential of 270 mV at 10 mA cm(-2) current density (eta (10)) and a high turnover frequency of over 2 s(-1) at 300 mV overpotential in 0.5 M H2SO4, a performance that surpasses that of commercial IrO2 significantly. Introducing the layer of amorphous WO3 between IrO2 nanoparticles and NC can distort the lattice of IrO2, exposing more highly active sites for water oxidation. The AWILD effect compensates for the lower Ir content and dramatically reduces the cost of the catalyst without sacrificing the catalytic activity. Additionally, this catalyst also exhibits high activity in acid for hydrogen evolution with only 65 mV of eta (10) attributed to the AWILD effect, exhibiting efficient bifunctionality as a Janus catalyst for overall water splitting. The AWILD approach provides a novel and efficient strategy for low-cost and highly efficient electrocatalysts for acidic overall water splitting with an extremely low content of noble metals.

Läs mer om Amorphous WO3 induced lattice distortion for a low-cost and high-efficient electrocatalyst for overall water splitting in acid

A Scandium MOF with an Unprecedented Inorganic Building Unit, Delimiting the Micropore Windows

2020. Pia Roenfeldt (et al.). Inorganic Chemistry 59 (13), 8995-9004

Artikel

A new scandium metal-organic framework (Sc-MOF) with the composition of [Sc(OH)(OBA)], denoted as Sc-CAU-21, was prepared under solvothermal reaction conditions using 4,4'-oxidibenzoic acid (H(2)OBA) as the ligand. Single-crystal structure determination revealed the presence of the new inorganic building unit (IBU) {Sc-8(mu-OH)(8)(O2C)(16)}. It is composed of cis-connected ScO6 polyhedra forming an eight-membered ring through bridging mu-OH groups. The connection of the IBUs leads to a 3D framework, containing 1D pores with a diameter between 4.2 and 5.6 angstrom. Pore access is limited by the size of the IBU, and in contrast to the isoreticular aluminum compound Al-CAU-21 [Al(OH)(OBA)], which is nonporous toward nitrogen at 77 K, Sc-CAU-21 exhibits a specific surface area of 610 m(2) g(-1). The title compound is thermally stable in air up to 350 degrees C and can be employed as a host for photoluminescent ions. Sc-CAU-21 exhibits a ligand-based blue emission, and (co)substituting Sc3+ ions with Ln(3+) ions (Eu3+, Tb3+, and Dy3+) allows the tuning of the emitting color of the phosphor from red to green. Single-phase white-light emission with CIE color coordinates close to the ideal for white-light emission was also achieved. The luminescence property was utilized in combination with powder X-ray diffraction to study in situ the crystallization process of Sc-CAU-21:Tb and Sc-CAU-21:Eu. Both studies indicate a two-step crystallization process, with a crystalline intermediate, prior to the formation of Sc-CAU-21:Ln.

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Metal-Organic Frameworks with Hexakis(4-carboxyphenyl)benzene

2020. Francoise M. Amombo Noa (et al.). Journal of the American Chemical Society 142 (20), 9471-9481

Artikel

Nine metal-organic frameworks have been prepared with the hexagon-shaped linker 1,2,3,4,5,6-hexakis(4-carboxyphenyl)-benzene (H(6)cpb) by solvothermal reactions in dimethylformamide (dmf) or dimethylacetamide (dmac) with acetic acid or formic acid as modulators: [Bi-2(cpb)(acetato)(2)(dmf)(2)]center dot 2dmf CTH-6 forms a rtl-net; 2(H2NMe2)[Cu-2(cpb)] CTH-7 forms a kgd-net; [Fe-4(cpb)-(acetato)(2)(dmf)(4)] CTH-8 and [Co-4(cpb)(acetato)(2)(dmf)(4)] CTH-9 are isostructural and form yav-nets; 2(HNEt3)[Fe-2(cpb)] CTH-10 and the two polymorphs of 2(H2NMe2)[Zn-2(cpb)]center dot 1.5dmac, Zn-MOF-888 and CTH-11, show kgd-nets; [Cu-2(cpb)-(acetato)(2)(dmf)(2)]center dot 2dmf, CTH-12, forms a mixed coordination and hydrogen-bonded sql-net; and 2(H2NMe2)[Zn-2(cpb)] CTH-13, a similarly mixed yav-net. Surface area values (Brunauer-Emmett-Teller, BET) range from 34 m(2) g(-1) for CTH-12 to 303 m(2) g(-1) for CTH-9 for samples activated at 120 degrees C in dynamic vacuum. All compounds show normal (10-fold higher) molar CO2 versus N-2 uptake at 298 K, except the 19-fold CO2 uptake for CTH-12 containing Cu(II) dinuclear paddle-wheels. We also show how perfect hexagons and triangles can combine to a new 3D topology laf, a model of which gave us the idea of foldable network topologies, as the laf-net can fold into a 2D form while retaining the local geometry around each vertex. Other foldable nets identified are cds, cds-a, ths, sqc163, clh, jem, and tfc covering the basic polygons and their combinations. The impact of this concept on breathing MOFs is discussed. I-2 sorption, both from gas phase and from MeOH solution, into CTH-7 were studied by time of flight secondary ion mass spectrometry (ToF-SIMS) on dried crystals. I-2 was shown to have penetrated the crystals, as layers were consecutively peeled off by the ion beam. We suggest ToF-SIMS to be a method for studying sorption depth profiles of MOFs.

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Switching O-O bond formation mechanism between WNA and I2M pathways by modifying the Ru-bda backbone ligands of water-oxidation catalysts

2021. Biaobiao Zhang (et al.). Journal of Energy Challenges and Mechanics 54, 815-821

Artikel

Understanding the seven coordination and O-O coupling pathway of the distinguished Ru-bda catalysts is essential for the development of next generation efficient water-oxidation catalysts based on earth-abundant metals. This work reports the synthesis, characterization and catalytic properties of a monomeric ruthenium catalyst Ru-bnda (H-2 bnda = 2,2'-bi(nicotinic acid)-6,6'-dicarboxylic acid) featuring steric hindrance and enhanced hydrophilicity on the backbone. Combining experimental evidence with systematic density functional theory calculations on the Ru-bnda and related catalysts Ru-bda (H(2)bda = 2,2'-bipyridine-6,6'-dicarboxylic acid), Ru-pda (H(2)pda = 1,10-phenanthroline-2,9-dicarboxylic acid), and Ru-biqa (H(2)biqa = (1,1'-biisoquinoline)-3,3'-dicarboxylic acid), we emphasized that seven coordination clearly determines presence of Ru-v =O with high spin density on the O-RuV=o atom, i.e. oxo with radical properties, which is one of the necessary conditions for reacting through the O-O coupling pathway. However, an additional factor to make the condition sufficient is the favorable intermolecular face-to-face interaction for the generation of the pre-reactive [Ru-V=O center dot center dot center dot O=Ru-V], which may be significantly influenced by the secondary coordination environments. This work provides a new understanding of the structure-activity relationship of water-oxidation catalysts and their potential to adopt I2M pathway for O-O bond formation.

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New Scandium-containing Coordination Polymers with Linear Linker Molecules

2020. Pia Rönfeldt (et al.). European Journal of Inorganic Chemistry 2020 (28), 2737-2743

Artikel

Two new scandium-containing coordination polymers, with the formulae {(CH3)2NH2}[Sc(BPDC)2] (1) and [Sc(OH) (BPyDC)] (2) were solvothermally synthesized by using the linear linker molecules biphenyl-4,4′-dicarboxylic acid (H2BPDC) and 2,2′-bipyridine-5,5′-dicarboxylic acid (H2BPyDC). Crystal structures were determined from single-crystal and powder Xray diffraction data, respectively. The crystal structures of 1 and 2 contain isolated ScO6 or chains of trans corner-sharing ScO6 octahedra as the inorganic building unit (IBU), which are connected by the linker molecules to a 3D framework or a layered structure, respectively. The compounds were characterized by IR-spectroscopy, elemental analysis, thermogravimetric analysis and photoluminescence spectroscopy. 1 shows blue emission at 400 nm, while 2 exhibits intense green emission at 550 nm with a high quantum yield (QY) of 69 %.

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Polymorphous Indium Metal-Organic Frameworks Based on a Ferrocene Linker

2020. Jannik Benecke (et al.). Inorganic Chemistry 59 (14), 9969-9978

Artikel

The metallocene-based linker molecule 1,1'-ferrocenedicarboxylic acid (H(2)FcDC) was used to synthesize four different polymorphs of composition [In(OH)(FeC12H8O4)]. Using conventional solvent-based synthesis methods and varying the synthetic parameters such as metal source, reaction temperature, and solvent, two different MOFs and one ID-coordination polymer denoted as CAU-43 (1), In-MIL-53-FcDC_a (2), and InFcDC (3) were obtained. Furthermore, thermal treatment of CAU-43 (1) at 190 degrees C under vacuum yielded a new polymorph of 2, In-MIL-53-FcDC_b (4). Both MOFs 2 and 4 crystallize in a MIL-53 type structure, but in different space groups C2/m for 2 and P (1) over bar for 4. The structures of the four title compounds were determined by single-crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD), or a combination of three-dimensional electron diffraction measurements (3D ED) and PXRD. N-2 sorption experiments of 1, 2, and 4 showed specific surface areas of 355 m(2) g(-)(1), 110 m(2) g(-1), and 140 m(2) g(-)(1), respectively. Furthermore, the electronic properties of the title compounds were characterized via Mossbauer and EPR spectroscopy. All Mossbauer spectra showed the characteristic doublet, proving the persistence of the ferrocene moiety. In the cases of 1, 3, and 4, appreciable impurities of ferrocenium ions could be detected by electron paramagnetic resonance spectroscopy. Cyclovoltammetric experiments were performed to demonstrate the accessible redox activity of the linker molecule of the title compounds. A redox process of FcDC(2-) with oxidation (between 0.86 and 0.97 V) and reduction wave (between 0.69 and 0.80 V) was observed.

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Observation of three different linker conformers in a scandium ferrocenedicarboxylate coordination polymer

2020. Jannik Benecke (et al.). CrystEngComm 22 (34), 5569-5572

Artikel

Electron and powder diffraction were combined to elucidate the structure of the new coordination polymer [Sc-2(FcDC)(3)] based on 1,1'-ferrocenedicarboxylate (FcDC(2-)), denoted as CAU-50. Remarkably, three different conformers of the very same linker molecule are observed, two of which serve as connectors for the scandium cations while one conformer acts as capping agent.

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Molecular Functionalization of NiO Nanocatalyst for Enhanced Water Oxidation by Electronic Structure Engineering

2020. Lizhou Fan (et al.). ChemSusChem 13 (22), 5901-5909

Artikel

Tuning the local environment of nanomaterial-based catalysts has emerged as an effective approach to optimize their oxygen evolution reaction (OER) performance, yet the controlled electronic modulation around surface active sites remains a great challenge. Herein, directed electronic modulation of NiO nanoparticles was achieved by simple surface molecular modification with small organic molecules. By adjusting the electronic properties of modifying molecules, the local electronic structure was rationally tailored and a close electronic structure-activity relationship was discovered: the increasing electron-withdrawing modification readily decreased the electron density around surface Ni sites, accelerating the reaction kinetics and improving OER activity, and vice versa. Detailed investigation by operando Raman spectroelectrochemistry revealed that the electron-withdrawing modification facilitates the charge-transfer kinetics, stimulates the catalyst reconstruction, and promotes abundant high-valent gamma-NiOOH reactive species generation. The NiO-C(6)F(5)catalyst, with the optimized electronic environment, exhibited superior performance towards water oxidation. This work provides a well-designed and effective approach for heterogeneous catalyst fabrication under the molecular level.

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A Stacking Faults-containing Silicogermanate with 24-ring Channels and Unbranched Zweier Silica Double Chains

Liqiu Tang (et al.). Crystal Growth & Design

Artikel

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Andrew Kentaro IngeResearcher

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Publikationer

Exploring the influence of atomic level structure, porosity, and stability of bismuth(iii) coordination polymers on electrocatalytic CO2 reduction

Toward Sustainable Li-Ion Battery Recycling

Metal-Dependent and Selective Crystallization of CAU-10 and MIL-53 Frameworks through Linker Nitration

Isoreticular Chemistry of Group 13 Metal-Organic Framework Compounds Based on V-Shaped Linker Molecules

3D electron diffraction as an important technique for structure elucidation of metal-organic frameworks and covalent organic frameworks

A Robust and Biocompatible Bismuth Ellagate MOF Synthesized Under Green Ambient Conditions

A Tunable Multivariate Metal-Organic Framework as a Platform for Designing Photocatalysts

Hexahydroxytriphenylene for the synthesis of group 13 MOFs - a new inorganic building unit in a beta-cristobalite type structure

An Expandable Hydrogen-Bonded Organic Framework Characterized by Three-Dimensional Electron Diffraction

Highly Diastereoselective Palladium-Catalyzed Oxidative Cascade Carbonylative Carbocyclization of Enallenols

Breathing Metal-Organic Framework Based on Flexible Inorganic Building Units

Permanent porosity and role of sulfonate groups in coordination networks constructed from a new polyfunctional phosphonato-sulfonate linker molecule

Silver-Triggered Activity of a Heterogeneous Palladium Catalyst in Oxidative Carbonylation Reactions

Water-based Synthesis and Properties of a Scandium 1,4-Naphthalenedicarboxylate

Catalytic Enantioselective Synthesis of Bicyclic Lactam N,S-Acetals in One Pot by Cascade Transformations

A Tetratopic Phosphonic Acid for the Synthesis of Permanently Porous MOFs

A metal-organic framework for efficient water-based ultra-low-temperature-driven cooling

Five New Coordination Polymers with a Bifunctional Phosphonate-Sulfonate Linker Molecule

Metal-Organic Frameworks as Catalysts for Organic Synthesis

In Situ XAS Study of the Local Structure and Oxidation State Evolutions of Palladium in a Reduced Graphene Oxide Supported Pd(II) Carbene Complex during an Undirected C−H Acetoxylation Reaction

Probing the active catalytic species generated from Pd(II)@MIL-101-NH2 in Heck coupling reactions: An operando X-ray absorption spectroscopy study

A Porous Cobalt Tetraphosphonate Metal-Organic Framework

Chemodivergent and Diastereoselective Synthesis of gamma-Lactones and gamma-Lactams

Design and synthesis of dopant-free organic hole-transport materials for perovskite solar cells

Lignin Based Molecular Materials - a Zinc Vanillate with a Hydrogen Bonded 4-and 8-connected Net with a New Topology

Multistimuli-Responsive Enaminitrile Molecular Switches Displaying H+-Induced Aggregate Emission, Metal Ion-Induced Turn-On Fluorescence, and Organogelation Properties

Probing the Evolution of Palladium Species in Pd@MOF Catalysts during the Heck Coupling Reaction: An Operando X-ray Absorption Spectroscopy Study

Solvent-Dependent Formation of Three New Bi-Metal-Organic Frameworks Using a Tetracarboxylic Acid

Synthesis, Transformation, Catalysis, and Gas Sorption Investigations on the Bismuth Metal-Organic Framework CAU-17

Versatile Heterogeneous Palladium Catalysts for Diverse Carbonylation Reactions under Atmospheric Carbon Monoxide Pressure

Elucidation of the elusive structure and formula of the active pharmaceutical ingredient bismuth subgallate by continuous rotation electron diffraction

A Water Based Synthesis of Ultrathin Hydrated Vanadium Pentoxide Nanosheets for Lithium Battery Application

A multi-purpose reaction cell for the investigation of reactions under solvothermal conditions

Effect of partial linker fluorination and linker extension on structure and properties of the Al-MOF CAU-10

Investigation of the effect of polar functional groups on the crystal structures of indium MOFs

Polymorphous Al-MOFs Based on V-Shaped Linker Molecules

Synthesis and crystal structure of three new bismuth(III) arylsulfonatocarboxylates

Unprecedented Topological Complexity in a Metal-Organic Framework Constructed from Simple Building Units

A Germanate with a Collapsible Open-Framework

Dihydroxybenzoquinone as Linker for the Synthesis of Permanently Porous Aluminum Metal-Organic Frameworks

Solving complex open-framework structures from X-ray powder diffraction by direct-space methods using composite building units

Catalytic Water Oxidation by Mononuclear Ru Complexes with an Anionic Ancillary Ligand

Open-Framework Germanates and Related Materials

A Highly Active Bifunctional Iridium Complex with an Alcohol/Alkoxide-Tethered N-Heterocyclic Carbene for Alkylation of Amines with Alcohols

A Stacking Faults-Containing Silicogermanate with 24-Ring Channels and Unbranched Zweier Silica Double Chains

Three Low-Dimensional Open-Germanates Derived from the 4^4 Net

Open-Framework Germanates

SU-62

SU-75

SU-65

The Structure of a Complex Open-framework Germanate Obtained by Combining Powder Charge-Flipping and Simulated Annealing

Investigation of the GeO2-1,6-Diaminohexane-Water-Pyridine-HF Phase Diagram Leading to the Discovery of Two Novel Layered Germanates with Extra-Large Rings

Synthesis and characterization of oligonuclear Ru, Co, and Cu oxidation catalysts

Open-Framework Germanate Built from the Hexagonal Packing of Rigid Cylinders

Promoting the Fe(VI) active species generation by structural and electronic modulation of efficient iron oxide based water oxidation catalyst without Ni or Co

Amorphous WO3 induced lattice distortion for a low-cost and high-efficient electrocatalyst for overall water splitting in acid

A Scandium MOF with an Unprecedented Inorganic Building Unit, Delimiting the Micropore Windows

Metal-Organic Frameworks with Hexakis(4-carboxyphenyl)benzene

Switching O-O bond formation mechanism between WNA and I2M pathways by modifying the Ru-bda backbone ligands of water-oxidation catalysts

New Scandium-containing Coordination Polymers with Linear Linker Molecules

Polymorphous Indium Metal-Organic Frameworks Based on a Ferrocene Linker

Observation of three different linker conformers in a scandium ferrocenedicarboxylate coordination polymer

Molecular Functionalization of NiO Nanocatalyst for Enhanced Water Oxidation by Electronic Structure Engineering

A Stacking Faults-containing Silicogermanate with 24-ring Channels and Unbranched Zweier Silica Double Chains

Investigation of the GeO₂-1,6-Diaminohexane-Water-Pyridine-HF Phase Diagram Leading to the Discovery of Two Novel Layered Germanates with Extra-Large Rings