POM-based inorganic–organic hybrid compounds: synthesis, structures, highly-connected topologies and photodegradation of organic dyes

Four new polyoxovanadate-based organic–inorganic hybrid materials [MnV2(bpp)2O6] (1), [Ag4V4(bpp)4O12]·2H2O (2) and [M3V6(bpp)4O18·4H2O]·2H2O [M = Ni (3), Zn (4), bpp = 1,3-bis(4-pyridyl)propane] have been synthesized under hydrothermal conditions through the self-assembly of transition metal salts, bpp ligands and ammonium metavanadate. Single-crystal X-ray diffraction analyses show that 1 possesses a three-dimensional framework, constructed from arrays of {V4O12} rings covalently linked through metal–organic units, {Mn(C13H4N2)2}. Compound 2 is an eight-connected self-catenated metal–organic framework, based on bimetallic {Ag4V4O12} clusters as nodes. Compounds 3 and 4 are isostructural, both of them exhibit an intriguing 6,10-connected network. The structure of 4, as an example, is based on single zinc atoms as six-connected nodes, as well as bimetallic {Zn2V6O18} clusters as ten-connected nodes, defining not only a new topology for three-periodic nets but also the first 6,10-connected framework using heterometallic clusters as nodes. Furthermore, the thermal stabilities and photocatalytic activities of 1–4 have been discussed in detail.