LAUSR

Five new polyoxometalate(POM)-based compounds, namely [CuII4(btmc)(ctcm)4(β-Mo8O26)]·[β-Mo8O26]·H2O (1), [CuII4(mct)2(ctcm)2(H2O)6(β-Mo8O26)]·[β-Mo8O26] (2), [CuII(dm4bt)(Mo3O10)] (3), [CoII(dm4bt)(Mo2O7)] (4) and [CoII(H2bdpm)(Mo2O7)] (5) (btmc = 1,4-bis(1,2,4-triazol-1-methyl)cyclohexane, mct = 4-(4-methyl-cyclohexylmethyl)-4H-[1,2,4]triazole, ctcm = C-(4-[1,2,4]triazol-4-ylmethyl-cyclohexyl)-methylamine, dm4bt = 2,2′-dimethyl-4,4′-bithiazole, and H2bdpm = 1,1′-bis(3,5-dimethyl-1H-pyrazolate)methane), were obtained through traditional hydrothermal methods and fully characterized by single-crystal X-ray diffraction analysis and IR spectroscopy. Compounds 1 and 2 show one-dimensional (1D) and two-dimensional (2D) structures, respectively, containing metal–organic chains. Compounds 3–5 are 1D, 1D and 2D structures, respectively, including infinite Mo–O chains. The title compounds can act as bi-functional electrochemical sensors to detect not only NO2− anions but also Cr(VI) cations, and especially compound 3 shows an excellent detection range and sensitivity for Cr(VI) and NO2−. Compound 3 also can act as a fluorescent sensor for the recognition of Hg2+. The fluorescence intensities can be reduced 65% by adding the solution of Hg2+ ions. So this series of POM-based compounds can be used as multi-functional photoelectric sensors for electrochemical sensing of NO2− and Cr(VI) and fluorescence sensing of Hg2+. Furthermore, the photocatalytic performances of compounds 1–5 were also studied.