Exchange of coordinated solvent during crystallisation of a metal-organic framework observed by in situ high energy X-ray diffraction

Using time-resolved monochromatic high energy X-ray diffraction, we present an in situ study of the solvothermal crystallisation of a new MOF [Yb2(BDC)3(DMF)2]⋅H2O (BDC=benzene-1,4-dicarboxylate and DMF=N,N-dimethylformamide) under solvothermal conditions, from mixed water/DMF solvent. Analysis of high resolution powder patterns obtained reveals an evolution of lattice parameters and electron density during the crystallisation process and Rietveld analysis shows that this is due to a gradual topochemical replacement of coordinated solvent molecules. The water initially coordinated to Yb3+ is replaced by DMF as the reaction progresses

Metal-organic frameworks from divalent metals and 1,4-benzenedicarboxylate with bidentate pyridine-N-oxide co-ligands

Two Co2+ metal-organic framework materials, constructed from a combination of 1,4-benzenedicarboxylate (BDC) and either 2,2′-dipyridyl-N-oxide (DPNO) or 2,2′-dipyridyl-N,N′-dioxide (DPNDO), are synthesized under solvothermal reaction conditions, and their structures solved by single crystal X-ray diffraction. Both have three-dimensional structures that contain octahedral Co2+ centers with μ2-(η2)-BDC, and bidentate DPNO or DPNDO coligands that bridge pairs of metal centers but do not contribute toward the overall connectivity of the framework. Co3(BDC)3(DPNO)2 contains trimers of trans corner-shared Co-centered octahedra with one type of bridging BDC ligand forming terminal edges of the trimers, bridging to neighboring trimer units, and a second type, bridging pairs of metals and also connecting neighboring trimers. Co2(BDC)2(DPNDO) is constructed from one-dimensional inorganic chains consisting of cis- and trans-corner shared Co2+-centered octahedra. The DPNDO ligand is bis-bidentate, forming the edges of one type of octahedron and the trans corners of the second type, with the coordination for both octahedra completed by bridging BDC linkers, which in turn connect the inorganic chains to yield a three-dimensional structure. Thermogravimetric analysis shows both materials contain trapped solvent, and while Co3(BDC)3(DPNO)2 is unstable with respect to solvent loss, Co2(BDC)2(DPNDO), and its magnesium analogue, can be desolvated to yield permanently porous materials that show thermal stability up to 300 °C. For Co2(BDC)2(DPNDO), gas adsorption studies show permanent microporosity with moderate uptake of small gas molecules (N2, CO2, CH4, and C2H6), supported by Grand Canonical Monte Carlo calculations based on the assumption of rigid crystal structures, while gravimetric analysis shows rapid and reversible methanol adsorption at ambient pressure for both the Co and Mg analogues of the framework.</p

Heterobimetallic sodium–lithium based metal–organic framework showing the β-cristobalite topology and having high permanent porosity

The solvothermal synthesis of a novel mixed-s-block metal–organic framework is described, with crystallization brought about by use of the sodium salt of the benzo-(1,2;3,4;5,6)-tris(thiophene-2′-carboxylate) linker in combination with a lithium salt. The structure of the material was determined by single-crystal X-ray diffraction, which reveals an expanded version of the β-cristobalite topology, with supertetrahedral building units made up of clusters of sodium and lithium ions. Outgassing under vacuum gives permanent porosity to the solid structure with a BET surface area of 1191 m2 g–1 measured by nitrogen adsorption.Peer Reviewe

Rapid and reversible formation of a crystalline hydrate of a metal-organic framework containing a tube of hydrogen-bonded water

The flexible metal-organic framework MIL-53(Cr) undergoes a dramatic volume expansion upon immersion in water at room temperature to form a crystalline hydrate in which water is held as a hydrogen-bonded tube: the hydration is readily reversible under ambient conditions as shown by time-resolved powder X-ray diffraction

MIL-53(Fe) : a good example to illustrate the power of powder diffraction in the field of MOFs

The field of “Metal-Organic Frameworks” (MOFs) has grown exponentially, giving rise to nanoporous materials with promising applications in gas storage, molecular separation or catalysis. Despite the use of solvothermal synthesis, some MOFs can be obtained only as polycrystalline samples and in those cases, powder diffraction is essential to characterize them. Herein, the nanoporous iron(III) terephthalate MIL-53(Fe), has been chosen to illustrate the power of powder diffraction in the field of MOFs. Its structure can be described as a one-dimensional channel system made up of trans-linked Fe octahedra, crosslinked by the bidentate dicarboxylate. Powder diffraction has been used to solve the structures of two MIL- 53(Fe) samples obtained with and without fluorine. Differences between the two structural models concern the occluded water molecules which are ordered in absence of fluorine and disordered in the other case. MIL-53(Fe) shows reversible dehydration-hydration behaviour, via a metastable anhydrous phase, yielding an anhydrous phase with reduced porosity compared to its chromium analogue. Finally, sorption of organic molecules (benzene, benzoquinone, pyridine and 2,6-lutidine) in MIL-53(Fe), studied by using powder diffraction data in order to understand the nature of the host-guest interactions, is discussed

Structural changes upon dehydration of Pr(III)(H2O){C6H3 (CO2)3} or MIL-81: A new three-dimensional praseodymium 1,2,4-benzenetricarboxylate with a one dimensional inorganic sub-network

75 FIELD Section Title:Crystallography and Liquid Crystals Institut Lavoisier, UMR CNRS 8180,Universite de Versailles St-Quentin en Yvelines,Versailles,Fr. FIELD URL: written in English.A new three-dimensional lanthanide(III) tricarboxylate, MIL-81 or Pr(III)(H2O)(C6H3-(CO2)3) has been obtained under hydrothermal conditions. Its three-dimensional structure, which has been detd. using X-ray powder diffraction data, is built-up from edge-sharing chains of nine coordinated praseodymium(III) capped square antiprisms linked through 1,2,4-Benzenetricarboxylate (1,2,4-BTC) moieties. Its thermal behavior has been investigated using TGA and X-ray thermo-diffractometry and reveals that dehydration is followed by an irreversible structural change giving the solid MIL-81ht or Pr(III)(C6H3 -(CO2)3) with both a change in the environment of the rare earth and in the connection mode of the carboxylate. Crystal data for MIL-81: monoclinic space group P21 with a = 10.272 (1) .ANG., b = 7.057 (1) .ANG., c = 6.232 (1) .ANG., b = 93.668 (4) Deg and Z = 2. Crystal data for MIL-81ht: triclinic space group P-1 with a = 9.864 (1) .ANG., b = 7.054 (1) .ANG., c = 5.784 (1) .ANG., a = 90.862 (9) Deg, b = 92.439 (6) Deg, g = 91.594 (8) Deg and Z = 2

An EXAFS study of the formation of a nanoporous metal-organic framework: evidence for the retention of secondary building units during synthesis

78 FIELD Section Title:Inorganic Chemicals and Reactions Institut Lavoisier, UMR CNRS 8637, Universite de Versailles St-Quentin en Yvelines, 45 Avenue des Etats-Unis,Versailles,Fr. FIELD URL: written in English.EXAFS data measured from amorphous intermediates and crystn. solns. provides the first evidence that trimeric iron oxide secondary building units remain intact during crystn. of the metal-org. framework MIL-89 from starting materials to products. [on SciFinder (R)

Synthesis and structure determination of new open-framework chromium carboxylate MIL-105 or CrIII(OH)·{O2C–C6(CH3)4–CO2}·nH2O

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