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

Abstract

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.