Photocatalytic C–H Bond Activation of Toluene on Rutile TiO2(110)

The activation of sp3 C–H bond over photoactive TiO2 catalysts has emerged as a promising means to realize the functionalization of hydrocarbons under mild conditions. However, a fundamental understanding of the microscopic mechanism is still unclear. In this work, we have systematically investigated the photochemistry of toluene on rutile (R)-TiO2(110) with temperature-programmed desorption (TPD) and density functional theory (DFT). The TPD results demonstrate that UV light (355 nm) efficiently facilitates the methyl C–H bond activation of toluene at 100 K, forming the stable C6H5CH2 group intermediate adsorbed on five-coordinated Ti4+ sites (Ti5c) until around room temperature (∼300 K). Further DFT calculations suggest that the photocatalytic C–H bond cleavage follow a homolytic manner via the formation of active benzyl radical (C6H5CH2 •). Our findings provide an insightful understanding of photocatalytic hydrocarbon functionalization on TiO2 catalysts.