科研之友
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摘要
Four polyoxometalate-based supramolecular assemblies were designed and synthesized under hydrothermal conditions: [Ni(2,2-bpy)(3)](5)[PW11NiO39(H2O)](2)center dot 1.08H(2)O (1), [Ni(2,2-bpy)(3)](1.5)[Ni(2,2bpy) (2)(H2O)BW12O40] (2), {[Ni(2,2-bpy)(3)](1.5)[Ni(2,2-bpy)(2)(H2O)GeW12O40]}(-) (3), and {[Ni(2,2-bpy)(3)](1.5)[Ni(2,2-bpy) (2)(H2O)PW12O40]}(2-) (4). These structures were characterized by IR, TG analysis, elemental analysis, Xray powder diffraction and single-crystal X-ray diffraction. In compound 1, two mono-substituted [PW11NiO39(H2O)](5-) anions were fused together via the H-bonding interactions forming a dimeric polyoxoanion [PW11NiO39(H2O)](2)(10-), which was surrounded by Ni-bpy cationic units into the molecular core-shell structures. Compounds 2-4 were composed of saturated polyoxoanions [BW12O40](5-), [GeW12O40](4-) and [PW12O40](3-), respectively. These saturated anions were surrounded by [Ni(2,2-bpy)(3)](2+) and [Ni(2,2-bpy)(2)(H2O)](2+) cationic units forming isostructural core-shell organic-inorganic hybrid materials. These isostructural polyoxometalates with different heteroatoms and charges all formed the isostructural materials, indicating that their charges do not have a significant influence on the structure of supramolecular assemblies. A detail study showed that substituted polyoxometalate with the terminal H2O molecule is essential for constructing the larger core-shell structure. An electrocatalytic study indicated that these four compounds are bifunctional electrocatalysts towards water oxidation and reduction of nitrite.
