Synthesis, Crystal Struture And Properties Research Of The Hybrid Materials Based On {BW₁₂} Building Blocks

The Keggin-type POM, is one of the most well-known classical structure. It is more likely to combine with dissimilar transition metals to form a number of novel structures compounds because the surface possesses a large of terminal and bridge oxygens. Such compounds have a wide range of applications in the fields of chemistry, materials and medicine etc. Due to the more negative surface charge density of the {BW12} unit, the metal ions are more favourable to forming hybrid multifunctional materials. Therefore, the article has synthesized nine organic-inorganic hybrid compounds by hydrothermal method based on {BW12} Keggin structure polyoxometalates and characterized by elemental analysis, IR, TQ UV and X-ray single crystal diffraction. Meanwhile, their electrochemical properties, electrocatalytic properties and photocatalytic properties have been investigated. The molecular formula of the nine compounds:(H2bibp)2[bibp{Cu(bipy)(bibp)}2{Cu(bipy)Cl}2{BWi204o}2]-3H20(l)[{Cu(bipy)2}(Cu(bipy)(Hbtb)}{BW12O40}] (2)[{Cu(bipy)2}2{Cu(bipy)(Hbib)}2{BWi204o}]-2H2O(3)[{Cu(bipy)2}4{Cu(bih)2}{BWi2O40}2] (4)[Zn(bipy)3]1.5[{Zn(bipy)2(H2O)}{BWi2O4o}}]·0.5H20 (5)[Co(bipy)3]1.5[{Co(bipy)2(H2O)[BW12O40}}] (6)[Ni(bipy)3]2[HBW12O40]H20 (7)[Cu(bipy)2]2{HBW12O40}] (8)[Cl{Cu(bipy)2}2][{Cu(bipy)2}{BW12O40}] (9) (bipy=2,2’-bipyridine, bibp=4,4’-bis(imidazolyl)biphenyl, btb=1,4-bis(1H-1,2,4-triazol-l-yl)benzene, bib=1,4-bis(1-imidazoly)benzene, bih=1,6-Bis(imidazoly)hexane)Single-crystal X-ray diffraction studies shows that compounds 1-9 are based on [BW12O40]5-cluster anion. Compounds 1-4 are modified by two different ligands. In compound 1, each [BW12O40]5- polyanion acts as bidentate ligand to link two types of Cu ions. Two {BW12} units linked by four Cu2+ and two bibp ligands, resulting in a pore structure unit, with the aperture of 19.188×25.841 A2. Two adjacent structural units are connected with {Cu-bibp-Cu} double-bridge to form a Z-type 1-D chain. The 2-D supramolecular layer can be formed by face-to-face π-π interactions. Supramolecular interactions between the layers to stabilize the 3-D hexagon pore supramolecular framework. In compound 2, two adjacent structural units connected by {Cu-btb-Cu} single-bridge generate a novel 1-D network. They are all through π-π stacking interactions or supramolecular interactions to construct two-dimensional (2-D) and three-dimensional (3-D) architectures. In compound 3, each [BW12O40]5- cluster anions connected by (Cu(2,2’-bipy)(bib)} group constitute a double polymers. This dimer looks like a "pendant" structure from ac side. The adjacent structure unit through hydrogen bonding interaction constitute one dimensional chain, through supramolecular role to form a three-dimensional network structure. In compound 4, each [BW12O40]5-cluster anions connected by{Cu(bimh)2} group constitute a double polymers. Thereby forming a three-dimensional (3-D) quadrilateral channel structure. Compound 5 and 6 are isostructural, In compound 5, the anion [BW12O40]5- serves as a monodentate ligand coordinating to a Zn centre through covalent bond between a terminal oxygen of the anion and the Zn centre. Compound 7 is supramolecular structure, which is composed of [BW12O40]5- cluster anions, two [Ni(2,2’-bipy)3]2+ units. And through supramolecular formed by the two-dimensional plane. Compound 8 is composed of [BW12O40]5- cluster anions, two [Cu(2,2’-bipy)3]2+units. Each [BW12O40]5- cluster anions through Cu-0 bonds constitute more infinite one-dimensional (1-D) chain. Compound 9 is consist of [BW12O40]5- cluster anions, one [Cu(2,2’-bipy)3]2+ units, [Cl{Cu(2,2’-bipy)2}2]3+ fragment and one water molecule of crystallization.Their electrochemical properties, electrocatalytic properties of synthesized compounds by cyclic voltammetry have been investigated. The results showed that compounds 1-9 have three pairs of redox peaks attributable to three redox processes of W atoms. Meanwhile all compounds plays an electric catalytic role in the reduction of H2O2. The degradation of RhB dye as probe reaction, meanwhile the light of the synthetic compounds are studied by the catalytic activity. The photocatalytic decomposition rates, defined as 1-C/Co, are 94.18%,90.64%.1.5%,95.2%,88.9%, 90.2%,94.2%,90.4% and 93.1%, respectively. The results indicated that synthetic compounds is an excellent photocatalytic degradation of RhB dye pollution materials, and plays an important role in environmental protection.