Highly crystalline lead-free Cs3Sb2Br9 perovskite microcrystals enable efficient and selective photocatalytic oxidation of benzyl alcohol

Selective oxidation of alcohols to the corresponding aldehydes constitutes a great challenge in organic and green chemistry, which typically requires environmentally unfriendly oxidants/catalysts or relatively harsh conditions (high temperature & pressure). Herein, we report an eco-friendly perovskite-based photocatalyst, in which all-inorganic perovskite Cs3Sb2Br9 microcrystals with high crystallinity were prepared using a facile antisolvent method at various temperatures. For the photocatalytic oxidation of benzyl alcohol, the Cs3Sb2Br9 microcrystal photocatalysts exhibited up to 77% conversion and 88% selectivity toward benzaldehyde under oxygen atmosphere and visible-light illumination. More significantly, the comparative experimental results in air were close to those in oxygen, with the observation of 96% conversion and 94% selectivity for the optimized conditions under air atmosphere. Notably, the conversion of our best-performing photocatalyst was 32 and 6.4 times higher than that of the lead-based CsPbBr3 and FAPbBr3 (FA: formamidinium) perovskites, respectively. Furthermore, the underlying photocatalytic oxidation mechanism was proposed by the electron spin resonance (ESR) and the controlled experiments using specific scavengers. This study sheds light on promising new photocatalytic applications of the lead-free metal halide perovskites.