Extended structure constructed from {Co7} cluster-containing sandwich-type polyoxometalate

Abstract

We report a new 2D layer-like network composed of Co7 cluster-containing sandwich-type polyoxometalate, Li10Na2[Co(H2O)3(CH3COO)]2{[Co7(H2O)4(OH)2(Ale)2][PW9O34]2}·20H2O (1) {H5Ale = Alendronic acid}, which was synthesized by the conventional aqueous solution method. Single-crystal X-ray diffraction analysis reveals that 1 crystallizes in the monoclinic P2(1)/n space group with unit cell a = 12.5391 (1) Å, b = 25.2531 (2) Å, c = 22.0462 (2) Å, β = 97.728(1)°, Z = 2, V = 6917.55 (10) Å3. This compound was further characterized by powder X-ray diffraction (PXRD), IR spectra and thermogravimetric (TG) analyses to confirm its structure and composition. As a result, polyoxoanion in 1 consists of two {A-PW9O34}9− units, which are fused together by a {Co7(H2O)4(OH)2(Ale)2} {Co7} cluster into a sandwich-type structure. In the {Co7} cluster, all the Co2+ ions are connected together by two Ale ligands and two OH groups into the hepta-nuclear cobalt cluster {Co7}. Further, the sandwich-type polyoxoanions are connected together by two {CH3CO2Co(H2O)3} units, resulting in the first 2D layer-like structure consisting of Co7-containing sandwich polyoxoanion. Electrochemical and electrocatalytic studies reveal that 1 exhibits good electrocatalytic activity toward the reduction of H2O2 in neutral aqueous solution.