Selective photocatalytic oxidation of benzyl alcohol to benzaldehyde or C-C coupled products by visible-light-absorbing quantum dots

This Forum Article describes the photocatalytic oxidation of benzyl alcohol by visible-light-absorbing colloidal CdS quantum dots (QDs), with 99% selectivity for benzaldehyde or 91% selectivity for C-C coupled products (primarily hydrobenzoin). The selectivity is tuned through the number of low-valent Cd atoms photodeposited on the surfaces of the QDs in situ; this deposition is enhanced by addition of a Cd²⁺ salt and suppressed by addition of an electron scavenger, anthroquinone-2-sulfonate, to the reaction mixture. In both cases, the external quantum efficiency (number of oxidative equivalents extracted from the QDs per incident photon) of the system is ∼1%.