| Four types of the solid poly.oxometalates (POM) such as microporous POM were prepared by the methods of sol-gel, anionic exchange and templating.The mixed oxides as synthesized materials are novel, water-insoluble, photochemically active and porous.Retention of the structure integrity of the starting POMs in the as-synthesized composites were confirmed by UV/DRS(DRS=Difruse Reflectance Spectrum), FT-IR, TG, XRD. However, chemical interactions were existed between POM molecules and silica network for the micro-and macroporous POM composites. The surface physicochemical properties, porous structures and surface morphology of the composites were comfirmed by the nitrogen adsorption measurements, surface characterization.lt was found that three composites have well-distributed porous channeled, and the average pore sizes are 22.46nm. Compared with starting material of POMs, BET surface areas of the POM-containing porous composites have been improved in the different extents.In water-methanol system, using 300-400nm ultraviolet rays, five complex heteropolyates, K6SiWnO39/SiO2(M=Mn, Ni, Co), K8SiW11O39/SiO2, and K4SiW12O40/SiO2, have been studied for water-decomposition. Results show that the complex heteropolyates loadend on SiO2 have less solubility and higher activity, especially those of lacunary, and that the hydrogen evolution rate can reach 6ml h-1. |
