Three-Dimensional Interpenetrating Frameworks Based on {P4Mo6} Tetrameric Clusters and Filled with In Situ Generated Alkyl Viologens.

Four novel three-dimensional interpenetrating frameworks based on {P4Mo6} units, H[C12H14N2]4[TM4(PO4)(H2O)4Na6][TM2(Mo6O12(HPO4)3(PO4)(OH)3)4]·8H2O (1, 2) and H[C14H18N2]4[TM4(PO4)(H2O)4Na6][TM2(Mo6O12(HPO4)3(PO4)(OH)3)4]·8H2O (3, 4) (TM = Co2+ (1, 3), Mn2+ (2, 4)) were synthesized and characterized using infrared spectroscopy, elemental analyses, thermogravimetric analysis, and single-crystal X-ray diffraction. In situ generated methyl viologen (compounds 1 and 2) or ethyl viologen (compounds 3 and 4) cations function as templates to induce the generation of 2-fold interpenetrating structures in which the {P4Mo6} tetrameric clusters with [TM4(PO4)Na6] (TM = Co2+ (1, 3) and Mn2+ (2, 4)) as the core were bridged by transition metal ions. Compounds 1-4 possess high thermal stabilities and the decomposition temperature of the inorganic frameworks were all >500 °C. It is worth noting that the four compounds all exhibited the bifunctional catalytic performance that they not only had an excellent photocatalytic activity for the reduction of hexavalent chromium (Cr(VI)) under visible light irradiation but also showed a good electrocatalytic activity for the reduction reaction of hydrogen peroxide.