Solvent-free aerobic photocatalytic oxidation of C(sp)-H and C(sp)-OH to C&z.dbd;O bonds

The development of highly active and selective photocatalytic systems for the oxidation of benzylic C(sp 3 )-H and C(sp 3 )-OH to C&z.dbd;O bonds under solvent-free conditions with molecular oxygen as an oxidant is attractive and challenging. In this study, a carbon- and PdO-doped Nb 2 O 5 -based catalyst (PdO/C-Nb 2 O 5 ) was designed and synthesized. This photocatalyst showed excellent solvent-free aerobic photocatalytic performances for two typical oxidation reactions of benzylic C(sp 3 )-H and C(sp 3 )-OH to C&z.dbd;O compounds. It was found that the doping of carbon and PdO in Nb 2 O 5 can modify its surface electrons, increase oxygen vacancies, and change the positions of its valence band and conduction band. Besides, the kinetic study showed that the oxidation of C-H in ethylbenzene to C-OH is the rate-limiting step in the two-step oxidation of ethylbenzene to acetophenone. Moreover, a photocatalytic reaction mechanism was proposed based on these experiments. In addition, the solvent-free aerobic photocatalytic oxidation system showed a good substrate tolerance for benzylic C(sp 3 )-H and C(sp 3 )-OH compounds with different substituents to the corresponding ketones and aldehydes. Solvent-free aerobic photocatalytic oxidation of benzylic C(sp 3 )-H and C(sp 3 )-OH to C&z.dbd;O bonds.