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.