Unveiling the role of Zn−N₁S₃ sites in atomic-precision ZnIn₂S₄/g-C₃N₄ heterostructure for highly efficient CO₂-to-CO conversion

Herein, for the first time, asymmetric zinc coordination sites (Zn−N₁S₃) were confined in ZnIn₂S₄ monolayer (NZIS_V) via N,N-Dimethylformamide/ethylene glycol (DMF/EG)-assisted hydrothermal method, overcoming the limitation of symmetric metal coordination in intrinsic ZnIn₂S₄. Through growing an NZIS_V on ultra-thin benzene-functionalized crystalline g-C₃N₄ nanosheets (CBCN), a delicately designed heterojunction was constructed with chemically bonded channels (In-N) and dislocation-induced tensile strain at the heterointerface. Consequently, the optimum catalyst achieves a superior CO₂-to-CO conversion efficiency of 166.5 μmol∙g⁻¹∙h⁻¹ with an apparent quantum yield of 5.4 % at 420 nm, outperforming the CO₂-to-CO conversion among all reported g-C₃N₄- and ZnIn₂S₄-based photocatalysts. The experimental techniques and theoretical simulations confirm that the modulated Z-scheme catalyst has maximum interfacial charge transfer efficiency. Furthermore, in situ-based characterization and computational calculations confirmed the highly activated/adsorbed CO₂ molecules and intermediates via the uniquely designed heterostructured catalyst. Also, Zn−N₁S₃ centers reduce the energy barrier formation of the key intermediate (^⁎COOH) and CO desorption via modulating the d-band center of the zinc atoms. This work underscores the crucial role of asymmetric active-site design in precisely modulated Z-scheme heterostructured materials for CO₂ conversion.