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We report the discovery and characterization of two porous Ce(III)-based metal–organic frameworks (MOFs) with the V-shaped linker molecules 4,4′-sulfonyldibenzoate (SDB2–) and 4,4′-(hexafluoroisopropylidene)bis(benzoate) (hfipbb2–). The compounds of framework composition [Ce2(H2O)(SDB)3] (1) and [Ce2(hfipbb)3] (2) were obtained by using a synthetic approach in acetonitrile that we recently established. Structure determination of 1 was accomplished from 3D electron diffraction (3D ED) data, while 2 could be refined against powder X-ray diffraction (PXRD) data using the crystal structure of an isostructural La-MOF as the starting model. Their framework structures consist of chain-like inorganic building units (IBUs) or hybrid-BUs that are interconnected by the V-shaped linker molecules to form framework structures with channel-type pores. The composition of both compounds was confirmed by PXRD, elemental analysis, as well as NMR and IR spectroscopy. Interestingly, despite the use of (NH4)2[CeIV(NO3)6] in the synthesis, cerium ions in both MOFs occur exclusively in the + III oxidation state as determined by X-ray absorption near edge structure (XANES) and X-ray photoelectron spectroscopy (XPS). Thermal analyses reveal remarkably high thermal stabilities of ≥400 °C for the MOFs. Initial N2 sorption measurements revealed the peculiar sorption behavior of 2 which prompted a deeper investigation by Ar and CO2 sorption experiments. The combination with nonlocal density functional theory (NL-DFT) calculations adds to the understanding of the nature of the different pore diameters in 2. An extensive quasi-simultaneous in situ XANES/XRD investigation was carried out to unveil the formation of Ce-MOFs during the solvothermal syntheses in acetonitrile. The crystallization of the two Ce(III)-MOFs presented herein as well as two previously reported Ce(IV)-MOFs, all obtained by a similar synthetic approach, were studied. While the XRD patterns show time-dependent MOF crystallizatio

Stable molecular clusters are of interest for targeted deposition in porous materials. In this work, we report the discovery of two new molecular Ce–O clusters of composition [Ce6O4(OH)4(NO3)4(DMF)4(C7H4O2X)8]·(DMF)4(H2O)2 (1-X) and [Ce6O4(OH)4(H2O)6(NO3)6(C7H4O2X)6] (2-X) (X = −Cl, −CHO, and −Br). Both cluster types contain a similar hexanuclear building unit, and crystal structures were determined from single-crystal X-ray diffraction or 3D electron diffraction data and subsequent Rietveld refinements against powder X-ray diffraction (PXRD) data. The crystal structure data is complemented by results from the local structure around the cerium ions, determined by extended X-ray absorption fine structure (EXAFS) measurements in the solid state. The composition of all Ce–O clusters was confirmed by elemental analysis, NMR and IR spectroscopy. The Ce–O clusters are highly soluble, up to 101 and 136 g/L for 1-Cl and 2-Cl, respectively, in organic solvents, which strongly depends on the type of cluster and functionalization of the benzoate ligands. Moreover, the structural and compositional integrity of dissolved clusters in different solvents was established. Recrystallization of 1-Cl from dichloromethane (DCM) and Raman spectroscopy confirm the integrity of both cluster types in solution. Further examination by EXAFS measurements on the Ce K-edge of clusters containing 4-chlorobenzoate reveals that only minor changes in the cerium environment of 1-Cl are observed upon dissolution in THF, DCM, and dioxane, while the results for 2-Cl indicate a partial degradation upon dissolution. After proving the stability, a cluster solution of 1-Cl was used to impregnate the mesoporous metal–organic framework Cr-MIL-101. Extensive characterization by PXRD, inductively coupled plasma-optical emission spectroscopy, and energy-dispersive X-ray spectroscopy, as well as thermogravimetry and N2-sorption measurements, confirm the successful insertion of Ce–O clusters into the large mesopor

The solution chemistry of aluminum is highly complex and various polyoxocations are known. Here we report on the facile synthesis of a cationic Al24 cluster that forms porous salts of composition [Al24(OH)56(CH3COO)12]X4, denoted CAU-55-X, with X=Cl−, Br−, I−, HSO4−. Three-dimensional electron diffraction was employed to determine the crystal structures. Various robust and mild synthesis routes for the chloride salt [Al24(OH)56(CH3COO)12]Cl4 in water were established resulting in high yields (>95 %, 215 g per batch) within minutes. Specific surface areas and H2O capacities with maximum values of up to 930 m2 g−1 and 430 mg g−1 are observed. The particle size of CAU-55-X can be tuned between 140 nm and 1250 nm, permitting its synthesis as stable dispersions or as highly crystalline powders. The positive surface charge of the particles, allow fast and effective adsorption of anionic dye molecules and adsorption of poly- and perfluoroalkyl substances (PFAS).

The use of the V-shaped linker molecules 4,4′-oxydibenzoic acid (H2ODB) and 4,4′-carbonyldibenzoic acid (H2CDB) led to the discovery of two isoreticular Ce(IV)-based metal–organic frameworks (MOFs) of composition [CeO(H2O)(L)], L = ODB2–, CDB2–, denoted CAU-58 (CAU = Christian-Albrechts-University). The recently developed Ce-MOF synthesis approach in acetonitrile as the solvent proved effective in accessing Ce(IV)-MOF structures with infinite rod-shaped inorganic building units (IBUs) and circumventing the formation of the predominantly observed hexanuclear [Ce6O8] cluster. For the structure determination of the isoreticular MOFs, three-dimensional electron diffraction (3D ED) and powder X-ray diffraction (PXRD) data were used in combination with density functional theory (DFT) calculations. [CeO(H2O)(CDB)] shows reversible H2O adsorption by stirring in water and thermal treatment at 190 °C, which leads to a unit cell volume change of 11%. The MOFs feature high thermal stabilities (T > 290 °C), which exceed those of most Ce(IV)-MOFs and can be attributed to the infinite rod-shaped IBU. Surface and bulk oxidation states of the cerium ions were analyzed via X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge spectroscopy (XANES). While Ce(III) ions are observed by the highly surface-sensitive XPS method, the bulk material contains predominantly Ce(IV) ions according to XANES. Application of the MOFs as catalysts for the catalytic degradation of methyl orange in aqueous solutions was also studied. While degradation activity for both MOFs was observed, only CAU-58-ODB revealed enhanced photocatalytic activity under ultraviolet (UV) light. The photocatalytic mechanism likely involves a ligand-to-metal charge transfer (LMCT) from the linkers to the Ce(IV) centers. Analyses by XANES and inductively coupled plasma-optical emission spectroscopy (ICP-OES) demonstrate that leaching of Cerium ions as well as partial reduction of Ce(IV) to Ce(III) takes plac

Solvothermal reaction of Bi(NO3)(3)center dot 5H(2)O with the flexible ligand 1,3,5-tris[4-(carboxyphenyl)oxamethyl]-2,4,6-trimethylbenzene (H3TBTC) in methanol at 120 degrees C for 1 h led to the formation of a novel coordination polymer (CP) with the composition of Bi(TBTC). The structure of the microcrystalline material was determined through threedimensional electron diffraction (3DED) measurements and phase purity was confirmed by a Pawley refinement, elemental analysis, and thermal analysis. The compound crystallizes in the triclinic space group P (1) over bar with one Bi3+ cation and one TBTC3- trianion in the asymmetric unit. Edge-sharing of BiO7 polyhedra leads to the formation of dinuclear Bi2O12 units, which through coordination to six TBTC3- ions form a layered two-periodic structure. Upon heating the material in air, the unit cell volume contracts by 9%, which is attributed to a shift in the inter-layer arrangement and to the flexibility of the building units of the structure. The compound starts to decompose at similar to 300 degrees C. Topological analysis revealed layers consisting of 3-c and 6-c nodes, consistent with the two-periodic kgd net - the dual of the Kagome net (kgm). However, due to the non-planar nature of the Bi(TBTC) layers, adjacent layers are interlaced by polycatenation.