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The new microporous metal organic framework [La2(H2O)5(H2TPPE)]·3H2O (CAU‐54), is obtained in a hydrothermal reaction of the linker 1,1,2,2‐tetrakis(4′‐phosphonophenyl)ethylene (H8TPPE) and La3+ ions. The extensive characterization including temperature‐dependent crystal structures and spectroscopic properties allowed to understand the unique, multi‐responsive material properties. CAU‐54 exhibits rarely observed reversible photochromism as well as turn‐on photoluminescence by various external chemical or physical stimuli including change of pressure, solvent exchange, and temperature variation. These properties can be unequivocally assigned to the presence of tetraphenylethylene (TPE) moieties of the linker molecules within the MOF, i.e., the ordered spatial arrangement of the linker molecules, the presence of accessible pores as well as the coordination flexibility of the phosphonate groups and the rotational freedom of the linker. By temperature‐dependent steady‐state and time‐resolved luminescence studies, it is shown that this compound exhibits a) blue fluorescence that becomes effectively quenched at room temperature, b) green efficient luminescence with thermal stability up to 400 K, and c) red phosphorescence correlated to the observed photochromism. In addition, CAU‐54 shows unusual thermal expansion properties as shown by temperature‐dependent powder X‐ray diffraction measurements with identified transition points that correlate with the observed temperature‐dependent changes in the photoluminescence. [ABSTRACT FROM AUTHOR]

Cerium‐based Metal‐Organic frameworks (Ce‐MOFs) are attracting increasing interest due to their similar structural features to zirconium MOFs. The redox behavior of Ce(III/IV) adds a range of properties to the compounds. Recently, perfluorinated linkers have been used in the synthesis of MOFs to introduce new characteristic into the structure. We report the synthesis and structural characterization of Ce(IV)‐based MOFs constructed using two perfluorinated alkyl linkers. Their structure, based on hexanuclear Ce6O4(OH)412+ clusters linked to each other by the dicarboxylate ions, has been solved ab‐initio from X‐ray powder diffraction data and refined by the Rietveld method. The crystallization kinetics and the MOF formation mechanism was also invesitigated by Synchrotron radiation with XAS spectroscopies (EXAFS and XANES). The MOFs present the same fcu cubic topology as observed in MOF‐801 and UiO‐66, and they showed good stability in water at different pH conditions. The electronic structure of these MOFs has been studied by DFT calculations in order to obtain insights into the density of states structure of the reported compounds, resulting in band gaps in the range of 2.8–3.1 eV. Their catalytic properties were tested both thermally and under visible light irradiation for the degradation of methyl orange (MO) dye. [ABSTRACT FROM AUTHOR]

Herein, we report two new COOH‐functionalized metal‐organic frameworks (MOFs) of composition [M6O4(OH)6(PMA)2(H2PMA)]×H2O, M=Zr, Hf), denoted CAU‐61, synthesized by using pyromellitic acid (H4PMA), a tetracarboxylic acid, as the linker and acetic acid as the solvent. The structure was determined from powder X‐ray diffraction data and one‐dimensional inorganic building units are connected through tetracarboxylate as well as dicarboxylate linker molecules, resulting in highly stable microporous framework structures with limiting and maximum pore diameter of ∼3.6 and ∼5.0 Å, respectively, lined with −COOH groups. Thermal stabilities of up to 400 °C in air, chemical stability in water at pH 1 to 12 and water uptake of 17 mol/mol prompted us to study the proton exchange of the μ2‐OH, μ3‐OH of the IBU and −COOH groups of the linker by titration with LiOH. Comparison of the pKa values with three UiO‐66 derivatives confirms distinct pKa value ranges and trends for the different acidic protons. Furthermore, the preparation of Zr−CAU‐61 membranes and first results on permeation of dyes and ions in aqueous solutions are presented. [ABSTRACT FROM AUTHOR]

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). [ABSTRACT FROM AUTHOR]

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A concept for obtaining isoreticular compounds with tri‐ instead of tetravalent metal cations using highly acidic reaction conditions was developed and successfully applied in a high throughput study using N,N′‐piperazinebis(methylenephosphonic acid) (H4PMP), that resulted in the discovery of a new porous aluminium phosphonate denoted CAU‐60⋅6 HCl. The high‐throughput study was subsequently extended to other trivalent metal ions. Al‐CAU‐60⋅6 HCl demonstrates reversible desorption of HCl (18.3 wt % loading) with three distinct compositions observed with zero, four or six HCl molecules per formula unit. Structural changes were followed in detail by powder X‐ray diffraction, EDX analysis as well as IR spectroscopy. Rapid desorption of HCl in water within minutes and subsequent adsorption from the gas phase and from aqueous solution are shown. Furthermore, it is possible to adsorb HBr into the guest free Al‐CAU‐60 framework, demonstrating the high stability of this compound. [ABSTRACT FROM AUTHOR]

Sonication-assisted liquid phase exfoliation was applied to six different layered coordination polymers (CPs) in aqueous surfactant solution. The resulting nanosheets were investigated for structural and compositional integrity and microscopic analysis gives insights into the relationship between the crystal structure of the materials and their exfoliability. Larger open pores seem to favour the production of nanosheets with higher aspect ratio of lateral size to thickness. [ABSTRACT FROM AUTHOR]

The tetraphosphonic acid 1,1,2,2‐tetrakis(4‐phosphonophenyl)ethylene (H8L) was used as linker in the synthesis of eight new isostructural, phosphonate‐based metal‐organic frameworks of composition [M2(H2O)2(H2L)] ⋅ xH2O (M=Y3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+, Yb3+, Lu3+; 1.5

The use of the linker molecule benzene‐1,3‐diphosphonic acid (H4L) and V4+‐ions in a hydrothermal synthesis without further additives led to the discovery of a new coordination polymer of composition [(VO)2(H2O)4(L)] ⋅ 2H2O. The structure of the compound was solved by direct methods from powder X‐ray diffraction data and refined using the Rietveld method. The compound was thoroughly characterized showing a reversible amorphization upon reduced pressure or high temperatures. A potential porosity was calculated, but could not be verified by H2O‐adsorption experiments. [ABSTRACT FROM AUTHOR]

The report is the first broader evaluation of the gas sorption properties of CAU‐23 for the adsorptives CO2, H2, CH4, and SO2. CAU‐23 is of intermediate porosity among Al‐MOFs with specific BET surface areas of the order of MIL‐100>MIL‐53>CAU‐23>MIL‐160>MIL‐53‐TDC>Alfum>CAU‐10‐H and total pore volumes of the order of MIL‐100>MIL‐53>CAU‐23>Alfum=MIL‐160>MIL‐53‐TDC>CAU‐10‐H. CO2 uptake (3.97 mmol g−1, 293 K) and H2 uptake (10.25 mmol g−1, 77 K) of CAU‐23 are second in the series and only slightly smaller than for MIL‐160. The CH4 uptake of CAU‐23 (0.89 mmol g−1, 293 K) is unremarkable in comparison with the other Al‐MOFs. The SO2 uptake (8.4 mmol g−1, 293 K) follows the porosity and higher SO2 uptakes were only observed for MIL‐53 and MIL‐100. CAU‐23 is one of the best Al‐MOFs for high‐pressure sorption of CO2, with an uptake of 33 wt.‐% at 20 bar, 293 K. Gas sorption measurements at two different temperatures gave near zero‐coverage enthalpy of adsorptions, ▵Hads0 for CO2 of −22 kJ mol−1 and of SO2 for −38 kJ mol−1 which is at the low end of the other Al‐MOFs (−22 to −39 kJ mol−1 for CO2; −41 to −51 kJ mol−1 for SO2), yet ▵Hads increases for CAU‐23 with CO2 and SO2 to −25 and −57 kJ mol−1, respectively. For CO2/CH4 and SO2/CO2 separation, ideal adsorbed solution theory (IAST) predicted gas selectivities of 5 and 27–50 (depending on molar ratio and model), respectively, in line with 4.5–6.3 and 17–50, respectively, with most of the other Al‐MOFs, where only MIL‐53‐TDC with 83 and MIL‐160 with 126 gave a higher SO2/CO2 selectivity at a molar ratio of 0.5. [ABSTRACT FROM AUTHOR]

The synthesis of iminobis(methylphosphonic acid) (H(sub 2)O(sub 3)PCH(sub 2))(sub 2)NH as a starting materialwas made to obtain barium bisphosphonate [Ba(sub 3)(C(sub 3)PCH(sub 2)NH(sub 2)CH(sub 2)PO(sub 3) as a pure metal. The barium bisphosphonate is an example of microporus inorganic-organic hybrid materials built up from flexible linkers.

15 Loiseau, T., Serre, C., Huguenard, C., Fink, G., Taulelle, F., Henry, M., Bataille, T., Férey, G. Chem. Eur. J. 2004, 10, 1373-1382; https://doi.org/10.1002/chem.200305413. 26 Li, W.-J., Liu, J., Sun, Z.-H., Liu, T.-F., Lü, J., Gao, S.-Y., He, C., Cao, R., Luo, J.-H. Nat. 6 García-Sánchez, A., Gomez-Mendoza, M., Barawi, M., Villar-Garcia, I. J., Liras, M., Gándara, F., de la Peña O'Shea, V. A. J. Am. Chem. Soc. 2020, 142, 318-326; https://doi.org/10.1021/jacs.9b10261. 5 Lamagni, P., Miola, M., Catalano, J., Hvid, M. S., Mamakhel, M. A. H., Christensen, M., Madsen, M. R., Jeppesen, H. S., Hu, X.-M., Daasbjerg, K., Skrydstrup, T., Lock, N. Adv. Funct. [Extracted from the article]