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 CO 2 photoreduction. In this work, a covalent triazine framework (CTF) combined with a Bi 19 S 27 Br 3 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 CO 2, stabilizes the intermediate state, and lowers the reaction energy barrier. Meanwhile, the chemically bonded interface favors rapid electron migration from Bi 19 S 27 Br 3 to CTF, as proved by ultrafast transient absorption spectroscopy and in situ irradiation XPS. As a result, CTF/Bi 19 S 27 Br 3 delivers a superior CO 2 photoreduction performance to yield CO (572.2 μmol g –1 h –1 ) in a pure water system, which is 38.6 times that of Bi 19 S 27 Br 3, 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.