CD3CN and NH3 interaction with Ti(IV) catalytic centres grafted on mesoporous MCM-41

CD3CN and NH3 were used as molecular probes to monitor the nature of both Bronsted and Lewis acid sites as well as the coordination sphere of Ti(IV) centres in Ti(IV) grafted MCM-41 by means of FT-IR and Diffuse Reflectance UV-Vis spectroscopies. CD3CN molecule was very effective to reveal the presence and the coordination changes of Ti(IV) Lewis acid centres, but was not helpful to evidence different type of OH acid centres in pure MCM-41 and Ti-MCM-41. On the contrary, ammonia adsorption on Ti-MCM-41 revealed the presence of Bronsted sites sufficiently acidic to protonate NH3 molecules with the formation of NH4+ species.