科研之友
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摘要
A series of basket-like heteropoly blues, formulated as (H(4)bth)[{Cu(H2O)}(2){Sr subset of (P6Mo2Mo16O73)-Mo-V-O-VI}]center dot 4H(2)O (1), {H2bih}(3)[{Fe-II(H2O)(2)}{Sr subset of (P6Mo2Mo16O73)-Mo-V-O-VI}]center dot 2H(2)O (2), (H(2)bih)(3)[{Co-II(H2O)(2)}{Sr subset of (P6Mo2Mo16O73)-Mo-V-O-VI}]center dot 2H(2)O (3), (H2bih)(3)[{Ni-II(H2O)(2)}{Sr subset of (P6Mo2Mo16O73)-Mo-V-O-VI}]center dot 2H(2)O (4), (H2bih)(2)(H2bip)[{Zn (H2O)(0.5)}{Sr subset of (P6Mo2Mo16O73)-Mo-V-O-VI}]center dot 5.5H(2)O (5), (bth = 1,6-bis(triazole) hexane; bih = 1,6-bis(imidazol) hexane; bip = 1,5-bis(imidazol) pentane) have been synthesized hydrothermally and fully characterized. The structural analysis shows that all the compounds contain two electron reduced polyanions [Sr subset of (P6Mo2Mo16O73)-Mo-V-O-VI](8-) (abbreviated as {P6Mo18O73}), which consists of a tetra vacant gamma-Dawson-type{P2Mo14} unit and a "handle"-shaped {P4Mo4} segment encapsulating a Sr2+ cation in the central cavity. Compound 1 is a 6-connected two-dimensional (2D) layer, which represents the first 2D assembly of basket-type polyoxometalates. Compounds 2-4 are isostructural one-dimensional zigzag chains linked by an M(H2O)(2) linker (M = iron for 2, cobalt for 3, and nickel for 4). Compound 5 is a dimeric cluster supported by a binuclear {Zn-2(H2O)} unit. The optical band gaps of 1-5 reveal their semiconductive natures. The compounds if used as photocatalysts exhibit a universal high efficiency degradation ability for dyes such as methylene blue, Rhodamine B, and Azon phloxine. The lifetime and reaction mechanism of the catalysts were investigated with a series of experiments. The compounds also show good bifunctional electrocatalytic behavior for the oxidation of ascorbic acid (AA) and reduction of nitrite ions.
