Two new 6-nitrobenzimidazole ligand-modified polymolybdate-based metal–organic complexes with excellent capacitive and electrocatalytic performances

By targeted introduction of 6-nitrobenzimidazole into polymolybdate, two new polymolybdate-based copper-organic complexes were successfully synthesized, namely {Cu2(6-nbm)4[β-Mo8O26](H2O)2}·(6-nbm)2·4H2O (1) and H2{Cu2(6-nbm)4[TeMo6O24](H2O)4}·(6-nbm)2·4H2O (2) (6-nbm = 6-nitrobenzimidazole), and structurally characterized by single-crystal X-ray diffraction, IR spectroscopy and powder X-ray diffraction (PXRD). Complexes 1 and 2 are both one-dimensional (1D) chain structures, in which 6-nbm hangs on the 1D chain in a monodentate coordination mode, appearing with a butterfly-like configuration. Complexes 1 and 2 both display bifunctional electrocatalytic activity toward the reduction of KNO2, as well as the oxidation of ascorbic acid (AA). The title complexes, used to prepare bulk-modified carbon paste electrodes (1–CPE and 2–CPE), can be used as electrochemical sensors, which show lower detection limit, good selectivity and anti-interference ability. In addition, the carbon cloth-based electrode modified with complex 1 (1–CC) exhibits ideal capacitance and long-term cycle stability, indicating that complex 1 can be a potential candidate for a pseudocapacitive material. In addition, complexes 1 and 2 show catalytic activity for the CO2 reduction reaction.