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Abstract: ZIF-76, Zn(Im) x (5-ClbIm) y (Im=imidazolate, 5-ClbIm=5-chlorobenzimidazolate), is, among the known ZIF structures, one of the few materials that combine a relatively large pore aperture with a large pore volume. Moreover, it is thermally stable up to 400°C and can be stored under ambient atmosphere without undergoing a measurable degradation. ZIF-76, therefore, appears to be an interesting material for applications in adsorption and separation. The published synthesis protocol leads to very low yields and is, thus, not applicable on a larger scale . In this work, we have succeeded in preparing ZIF-76 in suitable yields by changing the solvent and adding NaOH to the synthesis mixture. The addition of the base increases the yield and leads to smaller crystal sizes, by favoring nucleation over crystal growth. By using the same synthesis strategy, four new isomorphs of ZIF-76 were obtained, with different substituents on the benzimidazole ligand (Me, Br and NO2) and different metal sources (Co and Zn). All the samples were tested in the adsorption and separation of CO2/CH4 in order to highlight the influence of the linker and of the metal center on the adsorption/separation properties. [Copyright &y& Elsevier]

The amino modified MIL-68(In), hereafter denoted by MIL-68(In)_NH2, has been obtained by self-assembling from 2-amino-terephthalic acid and indium nitrate hydrate. The characterization of the modified material based on powder X-ray diffraction analysis, IR spectroscopy, 1H NMR spectroscopy and TG analysis demonstrates that this porous coordination network possesses the Kagomé topology of MIL-68(In) with amino modified pores walls. The Brunauer–Emmett–Teller surface area of 1230±24m2 g−1 for MIL-68(In)_NH2 compared to 1028±29m2 g−1 for MIL-68(In) exhibits an surface area improvement of approximate 200m2 g−1 within MIL-68(In)_NH2. Moreover, for both hybrids, the hydrogen and carbon dioxide sorption properties have been studied at 77K and 87K, and at 273K and 298K, respectively. The comparison of the corresponding results of MIL-68(In) shows that the presence of amino group can effectively enhance the adsorption enthalpy of H2 and CO2, whereas, slightly effect on the integral sorption amount. Besides, to our knowledge, it is the first time that the CO2 adsorption of MIL-68(In) sample are reported. [ABSTRACT FROM AUTHOR]