Benzoate acid-dependent formation of a series of interpenetrating metal–organic frameworks based on the cobalt∩1,4-bis(imidazolyl)benzene coordination substrate

Abstract

In this work, three structurally related aromatic polycarboxylic acids, 1,4-benzenedicarboxylic acid (H2bdc), 1,3,5-benzenetricarboxylic acid (H3btc), and 1,2,4,5-benzenetetracarboxylic acid (H4bttc), have been utilized as the ancillary ligands to perform a systematic study on the structure diversity of coordination polymer based on the Cobalt∩1,4-bis(imidazolyl)benzene matrix. The solvothermal reactions of Co(NO3)2 with the aromatic acids and bib ligand afford three novel coordination polymers, [Co(bib)(bdc)]∞ (1), {[Co3(btc)2(bib)2(H2O)2](H2O)2}∞ (2), and {[Co2(bttc)(bib)2](H2O)2}∞ (3). Compounds 1–3 illustrate a series of interpenetrating networks built up of different benzoate-bridging 1D chains. Owing to the different situation of the carboxylic group, the benzoates adopt bidentate linear, tridentate T-shaped and tetradentate double-track bridging modes to link metal centers into a W-type chain, ladder and double-center chain, respectively. These chains are further decorated by bib rods to afford a parallel interpenetrating (4,4) sheet for 1, and two three-fold interpenetrating α-Po networks based on different units for 2 and 3. The variety of structures and topologies indicates that aromatic acids play essential roles in the assembly of the final frameworks.