Preparation And Property Research Of Polyoxometalates-based Functional Materials

Polyoxometalates are a large group of nanoscale metal-oxygen clusters formed basically by molybdenum, tungsten and vanadium transition metals. Their chemical, physical and structural diversity have made them fascinating building units to construct functional materials which can be applied in many areas such as catalysis, magnetic, electronic, energy, medicine, imaging and photochromism. In the present work, we prepared two functional materials based on polyoxometalates by selective modification of polyoxometalates.1. A novel composite material based on polyoxometalates and titanium dioxide.For the first time, we chose Donor-π-bridge-acceptor type polyoxometalates and immobilized them on the surface of titanium dioxide nanoparticles through layer-by-layer method. The obtained hybrid materials POM@TiO2were characterized by Fourier transform IR spectroscopy (FTIR), Raman spectrum, Transmission electron microscopy, and energy dispersive X-ray spectroscopy. Besides, we also investigated their catalytic properties in treating organic pollutants (typically,10mg POM@TiO2can remove almost99.5%40mL20mg L-1methylene blue within3minutes under ambient conditions; moreover, the photodegradation efficiency of POM@TiO2was improved obviously compared to that of bare TiO2nanoparticles under visible irradiation).2. A new crown inorganic-organic hybrid material composed of the Keggin polyoxometalates and transition metal-amino acid coordination complexes.Compound K2{[KCu4(gly)4(OH)2(H2O)2Cl][PW12O40]}2·19H2O (1) was synthesized from the water solution and characterized by UV-visible spectroscopy, IR spectroscopy, TG analysis, elemental analysis and single crystal X-ray diffraction. Compound1possesses of a1D chain structure. Its crown-type monomer is built up with Keggin-type [PW12O40]3-polyoxometalates as building blocks and tetranuclear [KCu4(gly)4(OH)2(H2O)2Cl] rings as linkers. The [KCu4(gly)4(OH)2(H2O)2Cl] ring consists of four Cu2+ions and four gly ligands, which exhibits the crown ether feature after binding a potassium ion in its center. Further, two [KCu4(gly)4(OH)2(H2O)2Cl] rings connect with two Keggin polyoxoanions [PW12O40]3-and finally make the crown inorganic-organic hybrid material. Besides, magnetic study reveals the existence of ferromagnetic interactions within compound1.