Design and synthesis of purely inorganic 3D frameworks composed of reduced vanadium clusters and manganese linkers†
Two purely inorganic three-dimensional (3D) frameworks [Mn4(H2O)11VIV18O42(PO4)]7− (1) and [Mn2(H2O)7VIV18O42(PO4)]11− (2) were synthesized under hydrothermal conditions and fully characterized by single-crystal X-ray structural analysis, IR spectroscopy, thermogravimetric analysis and PXRD. Structural analysis revealed that these two compounds contained a similar all reduced polyoxoanion [VIV18O42(PO4)]15− linked by different amounts of manganese centers to form 3D framework materials. The V centers in these two compounds were all reduced to the +IV oxidation state, resulting in an all reduced polyoxoanion, which was firstly used as the building block for constructing 3D framework materials. The all reduced typical polyoxoanion [VIV18O42(PO4)]15− with 15 negative charges supplied enough charge amount to accept TM cations. In these two structures, the anions were surrounded by 12 and 5 Mn2+ ions, respectively, adjusted by varying the feeding amount of MnCl2·4H2O. An electrocatalytic study revealed that compound 1 exhibits electrocatalytic activity for reduction of H2O2.