Design and synthesis of purely inorganic 3D frameworks composed of reduced vanadium clusters and manganese linkers

Abstract

Two purely inorganic three-dimensional (3D) frameworks [Mn₄(H₂O)₁₁V^IV₁₈O₄₂(PO₄)]⁷⁻ (1) and [Mn₂(H₂O)₇V^IV₁₈O₄₂(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 [V^IV₁₈O₄₂(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 [V^IV₁₈O₄₂(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.