Immobilization of enzymes on an organic–inorganic hybrid network consisting of Dawson-type polyoxotungstate and a zinc(II)-biimidazole complex moiety

A new polyoxometalate (POM)-based organic–inorganic hybrid compound, {[(Zn(H2biim)2)3(P2W18O62)]·6H2O}n (1) (H2biim = 2,2′-biimidazole), has been hydrothermally synthesized and characterized by physico-chemical and spectroscopic methods. The structure of compound 1 exhibits a two-dimensional (2-D) network character, in which each Dawson-type polyoxoanion [P2W18O62]6− ({P2W18}) is connected with six [Zn(H2biim)2]2+ ({Zn(II)-H2biim}) complex fragments, while each {Zn(II)-H2biim} unit bridges two {P2W18} clusters, forming a 2-D network with a (6,3)-net topology. Compound 1 shows high enzyme-immobilizing capability for horseradish peroxidase (HRP). The maximum HRP load is 90.1 mg g−1 under optimal conditions. Furthermore, the immobilized enzyme (HRP/1) exhibits high catalytic activity and good stability, which can be applied to detect trace amounts of H2O2 in solution with a low detection limit of 3.11 × 10−3 mmol L−1.