2D/2D ZIF-L-Derived Znδ+ (0 ≤ δ ≤ 2) and N Codoped Carbon Skeleton@ZnIn2S4 S-Scheme Heterojunction for Solar-Driven CO2 Cycloaddition

Developing highly active photocatalysts that can directly utilize clean, cheap, and sustainable solar energy to achieve an efficient carbon dioxide (CO2) cycloaddition reaction under mild reaction conditions (1 bar of CO2) remains a great challenge. In this paper, 2D/2D ZnIn2S4/Zn-NC S-scheme heterojunction composites were constructed by the in situ growth of layered ZnIn2S4 on the surface of two-dimensional (2D) ZIF-L-derived Znδ+ (0 ≤ δ ≤ 2) and N codoped carbon skeletons (Zn-NC-T) via a low-temperature solvothermal method. The optimized ZnIn2S4/Zn-NC-T photocatalysts exhibited favorable photocatalytic CO2 cycloaddition performance, and the yield of cyclic carbonate reached about 98.8% under 10 mmol epoxides reactant, 1 bar CO2 pressure, and full-spectrum irradiation for 4 h. The favorable photocatalytic performance is attributed to the efficient photothermal conversion and effective separation of photogenerated carriers induced by the carbon matrix and heterojunctions, respectively. In addition, the stability of the heterojunction structure and activity were demonstrated through cyclic experiments. Furthermore, the possible mechanism of S-scheme heterojunction photocatalytic CO2 cycloaddition is proposed through electron paramagnetic resonance (EPR) spectra, cyclic voltammetry (CV) experiments, and quenching experiments. The mechanism analysis proved that light irradiation is conducive to the transfer of photogenerated electrons from the conduction band of ZnIn2S4 to epoxides, promoting the formation of ring-opening intermediates, and photogenerated holes may promote the coordination and polarization of adsorbed epoxides. This work not only prepared an S-scheme heterojunction catalyst with excellent photocatalytic CO2 cycloaddition performance but also provided new insights for the rational design of heterojunction catalysts for photocatalytic CO2 cycloaddition.