Low-Temperature Ethylbenzene Conversion on Rutile TiO₂(100) via Photocatalysis: The Strong Photon Energy Dependence

Direct dehydrogenation of alkanes under mild conditions offers a green route to produce valuable olefins, but realizing C-H bond activation at a low temperature presents a significant challenge. Here, photocatalytic ethylbenzene conversion into styrene has been achieved by one hole on rutile (R)-TiO₂(100) at 80 K under 257 and 343 nm irradiation. Although the rates of the initial α-C-H bond activation are nearly the same at the two wavelengths, the rate of the β-C-H bond cleavage is strongly dependent upon hole energy, leading to the much higher yield of 290 K styrene formation at 257 nm, which raises doubt about the simplified TiO₂ photocatalysis model in which excess energy of the charge carrier is useless and highlights the importance of intermolecular energy redistribution in photocatalytic reactions. The result not only advances our understandings in low-temperature C-H bond activation but also calls for the development of a more sophisticated photocatalysis model.