Selective photocatalytic oxidation of benzyl alcohol and its derivatives into corresponding aldehydes by molecular oxygen on titanium dioxide under visible light irradiation

The photocatalytic oxidation of benzyl alcohol and its derivatives, such as 4-methoxybenzyl alcohol, 4-chlorobenzyl alcohol, 4-nitrobenzyl alcohol, 4-methylbenzyl alcohol, 4-(trifluoromethyl)benzyl alcohol, and 4-tertiary-butylbenzyl alcohol, into corresponding aldehydes proceeded at high conversion and selectivity on a TiO2 photocatalyst under O2 atmosphere. The reaction was confirmed to proceed under irradiation with both UV-light and visible light. In particular, the visible light response was observed to be attributed to a characteristic surface complex formed by the adsorption of a benzyl alcoholic compound on the TiO2 surface. Here, the properties of the surface complex as the active center for this selective photocatalytic oxidation and the mechanism behind the reaction have been investigated.