Spatial Coupling of Photocatalytic CO2 Reduction and Selective Oxidation on Covalent Triazine Framework/ZnIn2S4 Core–Shell Structures

Abstract

Photocatalytic CO₂ reduction coupled with alcohol oxidation to aldehyde presents a promising strategy for the simultaneous production of fuels and valuable chemicals. The efficiency of the coupled photocatalytic reactions remains low due to poor charge separation, difficulty in CO₂ activation, and uncontrolled compatibility between reactions. This work presents S-bridged covalent triazine framework (SCTF) core-ZnIn₂S₄ shell photocatalysts for simultaneous CO₂ reduction and selective furfural synthesis at distinct active sites. As evidenced by in situ X-ray photoelectron spectroscopy and Kelvin probe force microscopy, photogenerated electrons in the composite photocatalysts transfer from the ZnIn₂S₄ shell to the SCTF core, improving charge separation. Experimental and theoretical results confirm that the presence of pyridine N atoms (Lewis basic sites) in SCTF enhances CO₂ adsorption, thereby reducing the energy barrier for *COOH generation and promoting *CO production. Meanwhile, furfuryl alcohol oxidation and deprotonation occur on ZnIn₂S₄ by consuming photogenerated holes, which in turn benefits the conversion of CO₂ to CO. As a result, the optimized SCTF/ZnIn₂S₄-0.2 core/shell photocatalyst exhibited a superior CO production yield of 263.5 µmol g⁻¹ and 95% conversion of furfuryl alcohol to aldehyde under simulated sunlight irradiation.