Designing multi-layered MOF-on-MOF-transformed core double-shell FeSx@ZnS@CoSx heterojunction for enhanced CO2 photoreduction with water vapor

The construction of core–shell structures derived from metal-organic framework (MOF) precursors is considered as a promising strategy for promoting photocatalytic CO2 reduction. Herein, a core double-shell structure catalyst (FeSx@ZnS@CoSx) has been rationally fabricated by ternary MOF-on-MOF synthetic strategies combined with subsequent sulfidation treatments. The obtained FeSx@ZnS@CoSx exhibited appealing activity for photocatalytic CO2 conversion with H2O vapor, affording a high CO generation rate of 69.90 μmol g−1 h−1 and CH4 generation rate of 2.01 μmol g−1 h−1. The outstanding performances could benefit from the distinctive core double-shell structure, which effectively formed dual type II charge transfer channels to improve the separation and migration of photogenerated carriers. Besides, the superstructure of CoSx species can provide abundant active sites to increase CO2 adsorption and meanwhile enhance the absorption spectrum in the visible light region, facilitating the CO2 conversion. The possible reduction pathways and key reaction intermediates were revealed by in situ DRIFTS results. This work offers a feasible ternary MOFs strategy to develop multi core–shell structures for high photocatalytic performance.