Structure and bifunctional electrocatalytic activity of a novel 3D framework based on dimeric monocopper-substituted polyoxoanions as ten-connected linkages

Abstract

A unique hybrid compound with dimeric monocopper-substituted Keggin polyoxoanions as ten-connected linkages, [Cu₅(en)₉][(PW₁₁CuO₃₉)₂]·18H₂O (1) (en = ethylenediamine), has been synthesized and characterized by elemental analysis, IR, TG analysis, powder X-ray diffraction and single-crystal X-ray diffraction. In 1, each dimeric Keggin [PW₁₁CuO₃₉]₂¹⁰⁻ cluster as an unusual deca-dentate connector links ten [Cu(en)₂]²⁺ complexes to form a three-dimensional (3D) framework with a (4⁴·8³²·12⁹) topology. The successful synthesis of 1 provides a feasible route for us to design and prepare high-connectivity and high-dimensionality hybrid compounds with the dimeric substituted polyoxoanions as linkages. Furthermore, the electrochemical studies have shown that 1 has bifunctional electrocatalytic activity towards not only the reduction of normal inorganic molecules hydrogen peroxide (H₂O₂) and potassium iodate (KIO₃) ascribed to the W-centers in [PW₁₁CuO₃₉]₂¹⁰⁻, but also the oxidation of biologic molecules ascorbic acid (AA) and dopamine (DA) ascribed to the Cu-centers in [Cu₅(en)₉][(PW₁₁CuO₃₉)₂]·18H₂O.