High-efficiency visible-light-driven oxidation of primary C-H bonds in toluene over a CsPbBr 3 perovskite supported by hierarchical TiO 2 nanoflakes.

Photocatalytic oxidation of toluene to valuable fine chemicals is of great significance, yet faces challenges in the development of advanced catalysts with both high activity and selectivity for the activation of inert C(sp 3 )-H bonds. Halide perovskites with remarkable optoelectronic properties have shown to be prospective photoactive materials, but the bulky structure with a small surface area and severe recombination of photogenerated electron-hole pairs are obstacles to application. Here, we fabricate a hierarchical nanoflower-shaped CsPbBr 3 /TiO 2 heterojunction by assembling CsPbBr 3 nanoparticles on 2D TiO 2 nanoflake subunits. The design significantly downsizes the size of CsPbBr 3 from micrometers to nanometers, and forms a type II heterojunction with intimate interfacial contact between CsPbBr 3 and TiO 2 nanoflakes, thereby accelerating the separation and transfer of photogenerated charges. Moreover, the formed hierarchical heterojunction increaseslight absorption by refraction and scattering, offers a large surface area and enhances the adsorption of toluene molecules. Consequently, the optimized CsPbBr 3 /TiO 2 exhibits a high performance (10 200 μmol g -1 h -1 ) for photocatalytic toluene oxidation with high selectivity (85%) for benzaldehyde generation under visible light. The photoactivity is about 20 times higher than that of blank CsPbBr 3 , and is among the best photocatalytic performances reported for selective oxidation of toluene under visible light irradiation.