Lead-free B-site bimetallic perovskite photocatalyst for efficient benzylic C–H bond activation

Summary: Although bismuth (Bi)-based halide perovskites have attracted profound attention in photocatalysis, the undesirable photophysical properties are not well modulated, and the effect of surface structure on adsorption and activation of reactant molecules is still unclear. Here, we report the structural design, via precise incorporation of antimony (Sb) atoms into the host lattice of Cs3Bi2Br9, of a series of B-site bimetallic perovskites (Cs3SbxBi2-xBr9, 0 ≤ x ≤ 2) with tunable band structures. The incorporation of Sb dramatically enhances the separation and transfer of photogenerated charges and prolongs their lifetimes. Considering these advantages, Cs3SbBiBr9 exhibits significantly enhanced photocatalytic activities in challenging benzylic C–H activation while maintaining a high selectivity of 96%. Theoretical calculations reveal that the introduction of Sb breaks the symmetry of the local structure and leads to asymmetric charge distribution that not only increases the adsorption capacity for methylbenzene but also reduces the energy barriers for C–H bond activation.