Solvent-free oxidation of benzylic C(sp3)–H bond over MA3Bi2Br9 perovskite photocatalyst by efficient singlet oxygen generation

Abstract

Photocatalytic selective oxidation under solvent-free conditions plays a pivotal role in green chemistry, which can diminish pollutant production and minimize resource consumption in chemical reactions. In this process, the activation of molecular oxygen (O2) plays a crucial role. Here, we demonstrate the efficient oxidation of C(sp3)–H bond in pure toluene to produce oxygenated products of benzaldehyde (BAD) and benzyl alcohol (BA) using O2 as an oxidant over lead-free MA3Bi2Br9 perovskite. Systematic spectroscopic characterizations and controlled experiments validate that MA3Bi2Br9 enables the activation of O2 to superoxide radical (•O2−) and singlet oxygen (1O2) via charged electron transfer and excitonic energy transfer, respectively. Significantly, 1O2 emerges as an important active species. The optimal photocatalytic performance delivered by MA3Bi2Br9 reaches a BAD generation rate of 10756 µmol g−1h−1, with a BAD product selectivity of 81.5 %. The performance is greater than most classical photocatalysts, representing one of the best photocatalytic activities available in the literature. The lead-free feature of MA3Bi2Br9 perovskite coupled with its impressive catalytic performance makes it promising for practical applications.