In situ growth of lead-free perovskite Cs2AgBiBr6 on a flexible ultrathin carbon nitride sheet for highly efficient photocatalytic benzylic C(sp3)-H bond activation

The selective conversion of organic pollutant toluene to high-value-added benzaldehyde and benzyl alcohol using green chemistry is of high research interest. However, the process remains challenging owing to the low adsorption of toluene molecules on the catalyst surface and the high dissociation energy of the C(sp3)-H bond. In this study, we developed an in situ assembly strategy to grow lead-free perovskite Cs2AgBiBr6 (CABB) on a flexible ultrathin carbon nitride sheet (UCNT) using an anti-solvent method, whereby a series of type II heter-ojunction structures of CABB-x@UCNT were constructed. This in situ preparation strategy enables UCNT to act as a nucleation site, thereby limiting the size of the CABB nanocrystals grown on it. In addition, the interfacial interaction between CABB and UCNT in the composite accelerates the separation of photogenerated carriers, which further facilitates electron-driven O2 reduction and hole-driven C(sp3)-H bond oxidation. Under simu-lated sunlight irradiation, the CABB-80@UCNT composite could effectively oxidize toluene to benzaldehyde and benzyl alcohol with a total conversion rate of 2630 mu mol g-1 h-1, which is 10.7 and 6 times higher that of UCNT and CABB, respectively, and the reaction selectivity exceeds 85%. Herein, we report that CABB-x@UCNT composites achieve efficient benzylic C(sp3)-H bond activation, expand the photocatalytic application of CABB, and provide new ideas for developing various types of in situ heterojunction systems.