Probing the titanium sites in Ti-MCM41 by diffuse reflectance and photoluminescence UV-Vis spectroscopies

Ti-MCM41 catalysts prepared by anchoring titanocene onto the inner walls of MCM-41 exhibit high catalytic performance in the epoxidation of cyclohexene and in oxidation of bulky cyclic and aromatic compounds because of the presence, as revealed by means of XANES and EXAFS spectroscopy, of a high concentration of accessible, well-spaced, and structurally well-defined Ti tetrahedral active sites (see Maschmeyer et al, Nature, 1995, 378, 159). These results have prompted us to study the nature and the coordinative environment of Ti active sites in MCM-41 also by means of diffuse reflectance UV-visible and luminescence spectroscopy. We revealed, particularly by means of photoluminescence spectroscopy, the presence of more than one bind of tetrahedral titanium site.