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 CABB-80@UCNT sample exhibits excellent photocatalytic performance for the oxidation of toluene, with a total conversion rate 10.7 and 6 times higher than that of UCNT and CABB, respectively, and its selectivity can exceed 85%. The outstanding performance of CABB-80@UCNT is attributed to the synergistic effect of size modulation and energy band engineering. • Lead-free perovskite Cs 2 AgBiBr 6 was in situ deposited on the surface of flexible ultrathin carbon nitride sheet UCNT. • A series of type II heterojunction structures of CABB-x@UCNT were constructed. • UCNT as a nucleation site results in size reduction of the CABB nanocrystals. • Interfacial CABB/UCNT interaction accelerates photogenerated carrier separation. • CABB-x@UCNT composites exhibit improved photocatalytic activity in toluene oxidation. 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(sp 3 )−H bond. In this study, we developed an in situ assembly strategy to grow lead-free perovskite Cs 2 AgBiBr 6 (CABB) on a flexible ultrathin carbon nitride sheet (UCNT) using an anti-solvent method, whereby a series of type II heterojunction 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 O 2 reduction and hole-driven C(sp 3 )−H bond oxidation. Under simulated sunlight irradiation, the CABB-80@UCNT composite could effectively oxidize toluene to benzaldehyde and benzyl alcohol with a total conversion rate of 2630 μmol 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(sp 3 )−H bond activation, expand the photocatalytic application of CABB, and provide new ideas for developing various types of in situ heterojunction systems.