Revealing the A‐Site Effect of Lead‐Free A 3 Sb 2 Br 9 Perovskite in Photocatalytic C(sp 3 )−H Bond Activation

Abstract The lead‐free halide perovskite A 3 Sb 2 Br 9 is utilized as a photocatalyst for the first time for C(sp 3 )−H bond activation. A 3 Sb 2 Br 9 nanoparticles (A 3 Sb 2 Br 9 NPs) with different ratios of Cs and CH 3 NH 3 (MA) show different photocatalytic activities for toluene oxidation and the photocatalytic performance is enhanced when increasing the amount of Cs. The octahedron distortion caused by A‐site cations can change the electronic properties of X‐site ions and further affect the electron transfer from toluene molecules to Br sites. After the regulation of A‐site cations, the photocatalytic activity is higher with A 3 Sb 2 Br 9 NPs than that with classic photocatalysts (TiO 2 , WO 3 , and CdS). The main active species involved in photocatalytic oxidation of toluene are photogenerated holes (h + ) and superoxide anions ( . O 2 − ). The octahedron distortion by A‐site cations affecting photocatalytic activity remains unique and is also a step forward for understanding more about halide‐perovskite‐based photocatalysis. The relationship between octahedron distortion and photocatalysis can also guide the design of new photocatalytic systems involving other halide perovskites.