Boosting Photocatalytic Activity and Stability of Lead-Free Cs₃Bi₂Br₉ Perovskite Nanocrystals via In Situ Growth on Monolayer 2D Ti₃C₂T_x MXene for C–H Bond Oxidation

Light-driven selective oxidation of saturated C–H bonds with molecular oxygen, as an alternative to conventional thermochemical catalysis, allows a sustainable and eco-friendly manner to convert solar energy into highly value-added oxygenates. However, the photocatalytic oxidation of hydrocarbons still remains a great challenge owing to the low efficiency in the separation and transfer of photogenerated charge of the currently available photocatalytic materials. Herein, we report a novel perovskite-based heterostructure photocatalyst, in which ligand- and lead-free all-inorganic perovskite Cs3Bi2Br9 nanocrystals (NCs) with uniform crystal size and high crystallinity were homogeneously distributed on the surface of ultrathin two-dimensional (2D) monolayer Ti3C2Tx MXene nanosheets in an in situ growth manner. The resultant heterostructure featured with intimate interface between Cs3Bi2Br9 NCs and Ti3C2Tx MXene and strong visible-light adsorption not only exhibits significant enhancement in the performance of photocatalytic oxidation of challenging aromatic and aliphatic alkanes under visible-light irradiation but also greatly improves the stability of Cs3Bi2Br9 NCs under a reaction environment. Comprehensive characterizations reveal that the formation of an intimate interface between Cs3Bi2Br9 NCs and highly conductive ultrathin 2D Ti3C2Tx MXene nanosheets via strong interaction markedly accelerates the separation and transfer efficiency of photogenerated electron–hole pairs and simultaneously suppresses their recombination, resulting in improved utilization of the excited charges, which account for the highly enhanced photocatalytic performance.