Strongly Coupled Interface in Electrostatic Self-Assembly Covalent Triazine Framework/Bi19S27Br3 for High-Efficiency CO2 Photoreduction

Constructing a strong bonded interface is highly desired to build fast charge-transfer channels and tune reactive sites for optimizing CO2 photoreduction. In this work, a covalent triazine framework (CTF) combined with a Bi19S27Br3 heterojunction is designed using an electrostatic self-assembly process. Due to the oppositely charged states between two components and ultrasonic treatment, a strong coupled interface is realized with the formation of Bi–C/N/O bonds, leading to robust interfacial polarization. This feature causes interfacial charge redistribution, intensifies the interaction between triazine N reactive sites and CO2, stabilizes the intermediate state, and lowers the reaction energy barrier. Meanwhile, the chemically bonded interface favors rapid electron migration from Bi19S27Br3 to CTF, as proved by ultrafast transient absorption spectroscopy and in situ irradiation XPS. As a result, CTF/Bi19S27Br3 delivers a superior CO2 photoreduction performance to yield CO (572.2 μmol g–1 h–1) in a pure water system, which is 38.6 times that of Bi19S27Br3, with apparent quantum yields up to 7.9 and 6.2% at 380 and 400 nm, respectively. This strong interfacial coupling strategy provides an accessible pathway to designing interfacial polarized, high-efficiency photocatalysts.