Four new MOFs based on an imidazole-containing ligand and multicarboxylates: syntheses, structures and sorption properties

Four new complexes have been synthesized by solvothermal reactions of an imidazole-containing ligand 3,3',5,5'-tetra(1H-imidazol-1-yl)-1,1'-biphenyl (L) with corresponding metal salts via the alternation of auxiliary multicarboxylates, [Zn-2(L)(2,6-NDC)(OAc)(2)]center dot 2H(2)O (1), [Zn-2(L)(BPnDC)(2)]center dot 6H(2)O (2), [Co-2(L)(OBA)(2)]center dot 8H(2)O (3) and [Zn-4(L)(2)(ODAC)(2)]center dot 2MeCN center dot 5H(2)O (4) (2,6-H2NDC = 2,6-naphthalic acid, H(2)BPnDC = 4,4'-carbonyldibenzoic acid, H(2)OBA = 4,4'-oxidibenzoic acid, and H(4)ODAC = 3,3',4,4'-oxidibenzene tetracarboxylic acid). The complexes were characterized by single crystal and powder X-ray diffractions, IR, elemental and thermogravimetric analysis. All of them possess different three-dimensional (3D) frameworks based on M(II)-L two-dimensional layers, which are further connected by auxiliary dicarboxylates with distinct bridging-angles and coordination numbers to obtain the final frameworks. Complex 1 is a (3,4)-connected 3D framework with gwg topology, while 2 and 3 are isostructures with a (4,4)-connected 2-fold interpenetrating 3D net. In the case of 4, it possesses a (4,4,4,4)-connected 3D architecture with a new topology. The desolvated samples 2' and 3' have adsorption capacities of H2O/MeOH/EtOH, while sample 4 has remarkable selective adsorption for H2O/MeOH over EtOH.