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

Abstract

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, [Zn₂(L)(2,6-NDC)(OAc)₂]·2H₂O (1), [Zn₂(L)(BPnDC)₂]·6H₂O (2), [Co₂(L)(OBA)₂]·8H₂O (3) and [Zn₄(L)₂(ODAC)₂]·2MeCN·5H₂O (4) (2,6-H₂NDC = 2,6-naphthalic acid, H₂BPnDC = 4,4′-carbonyldibenzoic acid, H₂OBA = 4,4′-oxidibenzoic acid, and H₄ODAC = 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.