Enhancing Isolated Ti (IV) Framework Sites in HMS*

Ti-HMS materials were prepared by grafting titanocene onto the inner walls of hexagonal mesoporous silica (HMS). The materials were characterized via powder X-ray diffraction, N2 adsorption-desorption isotherms, diffuse reflectance UV-Vis spectroscopy, and thermo-gravimetric analysis. The template of HMS was removed by calcination, ethanol-extraction, and ethanol-extraction followed by hydrolysis. The available grafting sites of OH groups depend on the different template removal methods of HMS. Ethanol-extraction followed by hydrolysis favors site-isolated Ti atoms in HMS. The catalytic performances of Ti-HMS materials were tested in the oxidation of 4-tert-butyltoluene with aqueous hydrogen peroxide. Ti-HMS prepared from HMS via the processing of ethanol-extraction followed by hydrolysis as support gave a maximum conversion of 7.5% and a complete selectivity to 4-tert-butyl-benzaldehyde, and showed a higher activity compared with those prepared by calcination and ethanol-extraction.