Microwave-assisted synthesis of nioboorganosilicates and microwave-accelerated catalytic activity of thereof

A novel type of organic-inorganic hybrid mesoporous material, i.e., mesoporous silica with organic groups and niobium species as lattice fundamentals was prepared. This new material was synthesized by self-assembly of bridged silsesquioxane precursor containing ethane-bridging group that connects two silicon atoms to surpass an oxygen atom in the mesoporous framework. They had been synthesized by using nonionic template Pluronic P123 as a structure-directing agent under microwave irradiation. The properties of obtained materials were confirmed by X-ray diffraction (XRD), transmission electron microscopy (TEM), adsorption measurements, DTG/TG, DR-UV-vis, Raman and FTIR spectroscopies. The Nb-PMOs were tested in the oxidation reaction of cyclohexene to epoxide in the liquid phase using hydrogen peroxide as an oxidant. The reaction took place under conventional thermal heating and for comparison in the presence of microwaves. The microwave-assisted cyclohexene oxidation over nioboorganosilicates was completed within 1 h in comparison to 36-40 h for conventional method with comparable conversion and slightly higher selectivity to cyclohexene epoxide. (C) 2008 Elsevier B.V. All rights reserved.