Constructing vacancy-decorated heterojunction photocatalysts is a feasible strategy for highly efficient photooxidation of toluene to benzaldehyde. However, poor interface interaction and vacancy-triggered mismatched redox kinetics seriously impede photocatalytic activity improvement. Herein, a chemically bonded Cs₃Bi₂Br_9–x@AgBr core–shell heterojunction with unified adsorption-redox sites is fabricated via an in-situ light-assisted Ag⁺ insertion method. Experiments and theoretical calculations demonstrate that the type-II band alignment with interfacial Bi–Br–Ag bonds boosts the charge separation. Moreover, because of the greater oxygen adsorption energy and the steric-hindrance effect of the AgBr shell, the preferred adsorption site of O₂ is modulated from Br vacancy (V_Br, trapping holes) to its corresponding reduction site (AgBr, gathering electrons), thereby ensuring V_Br-enhancing toluene adsorption/oxidation on Cs₃Bi₂Br₉. Therefore, Cs₃Bi₂Br_9–x@AgBr exhibits an improved benzaldehyde production rate of 5.61 mmol g^–1 h^–1 (selectivity: 91%), outperforming pure Cs₃Bi₂Br₉ by a factor of 6. This work underlines the importance of the rational design of vacancy-decorated heterointerface and redox sites at the atomic level in photocatalysis.

中文翻译：

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调节 Cs3Bi2Br9–x@AgBr 核壳异质结构的吸附氧化还原位点和电荷分离用于选择性甲苯光氧化

构建空位修饰的异质结光催化剂是甲苯高效光氧化制苯甲醛的可行策略。然而，较差的界面相互作用和空位引发的氧化还原动力学失配严重阻碍了光催化活性的提高。在此，通过原位光辅助Ag ⁺插入方法制备了具有统一吸附氧化还原位点的化学键合Cs ₃ Bi ₂ Br _{9– x} @AgBr核壳异质结。实验和理论计算表明，II 型能带与界面 Bi-Br-Ag 键的排列可促进电荷分离。此外，由于AgBr壳层具有较大的氧吸附能和空间位阻效应，O _{2的优先吸附位点从Br空位（V Br} ，捕获空穴）调整到其相应的还原位点（AgBr，聚集电子） ，从而确保V _{Br增强Cs 3} Bi ₂ Br ₉上的甲苯吸附/氧化。因此，Cs ₃ Bi ₂ Br _{9– x} @AgBr 的苯甲醛生产率提高到 5.61 mmol g ^–1 h ^–1（选择性：91%），比纯 Cs ₃ Bi ₂ Br ₉提高了 6 倍。这项工作强调了光催化中原子水平上合理设计空位修饰异质界面和氧化还原位点的重要性。