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.