Ionic liquid-assisted preparation of lead-free Cs3Bi2Br9 perovskite with high stability for selective photocatalytic oxidation of benzyl alcohol

Metal e Metal halide perovskites (MHPs) have stand out as a photocatalyst because of their excellent optical property. However, the main drawbacks of MHPs are their instability resulted from their ionic nature, and the toxicity of Pb in popular lead halide perovskite. To solve these problems, in this work, we choose Cs3Bi2Br9 as a typical lead-free MHPs, and prepared Cs3Bi2Br9 using ionic liquids 1-decyl-3-methylimidazolium bromide ([Dmim]Br) as the surface ligands and bromine source through ligand-assisted reprecipitation method. The prepared Cs3Bi2Br9 NCs remained stable under light, heat and moisture, which is attributed to the anchoring of ionic liquid [Dmim]Br on the nanocrystalline surface to passivates the harmful defects. Then, we select oxidation of benzyl alcohol as a representative model reaction and investigated the photocatalytic performance of Cs3Bi2Br9 NCs. Under the illumination of visible light, benzyl alcohols can be transformed at the presence of Cs3Bi2Br9 NCs into corresponding aldehydes with near 100% selectivity and 99.64% conversion in 1 h. The radical scavenging experiments, spectroscopic analysis, and EPR measurements confirmed that the main active species responsible for highly selective oxidation were singlet oxygen 1O2, which were proved to be generated from the transformation of superoxide radicals •O2−. This work is expected to provide insights for extending the design and photocatalytic applications of lead-free MHPs NCs.