Characterization of titanium-containing mesoporous silica molecular sieve SBA-15 and generation of paramagnetic hole and electron centers

Abstract

Titanium has been incorporated into mesoporous silica molecular sieve SBA-15 via incipient-wetness impregnation with titanium isopropoxide in ethanol followed by calcination. Characterization results suggest that at low titanium loading the titanium is monoatomically dispersed in the silica framework. This isolated titanium species reaches a maximum concentration around 6 at.% relative to silicon. At higher titanium loading titanium dioxide (anatase) is formed. The materials with significant titanium dioxide formation have reduced pore diameters which suggests that the titanium dioxide exists as a thin film anchored inside the mesopores of SBA-15. Dehydration of this TiO2/SBA-15 material forms paramagnetic oxygen hole centers and two types of Ti(III) centers.