Oxygen vacancy in lead‐free perovskite Cs ₂ AgBiBr ₆ /WO _{3‐ <i>X</i>} for enhanced photocatalytic C(sp ³ )‐H bond oxidation

Abstract Photocatalytic oxidation of toluene to valuable benzaldehyde offers a promising pathway for sustainable production of fine chemicals and pharmaceuticals. In this process, photogenerated holes play a crucial role in C(sp 3 )‐H bond dissociation. However, the photocatalytic performance of current photocatalysts is often hindered by the low separation and transfer efficiency of photogenerated charges. In this work, we presented a perovskite‐based heterostructure via in situ growth of defective WO 3‐ x nanosheets on Cs 2 AgBiBr 6 nanoparticles for photocatalytic toluene transformation. In situ Fourier transform infrared spectroscopy tests proved the introduction of oxygen‐deficient WO 3‐ x component enhanced the chemisorption of molecular oxygen. The in situ electron paramagnetic resonance and 4‐chloro‐7‐nitro‐1,2,3‐benzoxadiazole fluorescence measurements further confirmed the presence of oxygen vacancies, and the formation of heterostructure synergistically accelerated the formation of the superoxide radicals and the transfer of photogenerated charge carriers. Under visible light irradiation, Cs 2 AgBiBr 6 /WO 3‐ x photocatalyst could effectively oxidize toluene toward benzaldehyde with a conversion rate of 9020 μmol g −1 h −1 , which was a 3.5‐fold increase over that of the unmodified Cs 2 AgBiBr 6 .