Structural analysis of interpenetrated methyl‐modified MOF‐5 and its gas‐adsorption properties

The first example of an interpenetrated methyl-modified MOF-5 with the formula Zn4O(DMBDC)3(DMF)2, where DMBDC2- is 2,5-dimethylbenzene-1,4-dicarboxylate and DMF is N,N-dimethylformamide (henceforth denoted as Me2MOF-5-int), namely, poly[tris(μ4-2,5-dimethylbenzene-1,4-dicarboxylato)bis(N,N-dimethylformamide)-μ4-oxido-tetrazinc(II)], [Zn4(C10H8O4)3O(C3H7NO)2]n, has been obtained from a solvothermal synthesis of 2,5-dimethylbenzene-1,4-dicarboxylic acid and Zn(NO3)2·6H2O in DMF. A systematic study revealed that the choice of solvent is of critical importance for the synthesis of phase-pure Me2MOF-5-int, which was thoroughly characterized by single-crystal and powder X-ray diffraction (PXRD), as well as by gas-adsorption analyses. The Brunauer-Emmett-Teller surface area of Me2MOF-5-int (660 m2 g-1), determined by N2 adsorption, is much lower than that of nonpenetrated Me2MOF-5 (2420 m2 g-1). However, Me2MOF-5-int displays an H2 uptake capacity of 1.26 wt% at 77 K and 1.0 bar, which is comparable to that of non-interpenetrated Me2MOF-5 (1.51 wt%).