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

[Display omitted] • A ternary MOF-on-MOF strategy was introduced to synthesize the core double-shell FeS x @ZnS@CoS x catalyst. • FeS x @ZnS@CoS x exhibited the excellent catalytic activity for the CO 2 photoreduction. • FeS x @ZnS@CoS x structure with dual type II heterojunctions improved the separation of electron-hole pairs. • The superstructure of CoS x species provided abundant active sites and broadened light absorption capacity. The construction of core–shell structures derived from metal-organic framework (MOF) precursors is considered as a promising strategy for promoting photocatalytic CO 2 reduction. Herein, a core double-shell structure catalyst (FeS x @ZnS@CoS x) has been rationally fabricated by ternary MOF-on-MOF synthetic strategies combined with subsequent sulfidation treatments. The obtained FeS x @ZnS@CoS x exhibited appealing activity for photocatalytic CO 2 conversion with H 2 O vapor, affording a high CO generation rate of 69.90 μmol g−1 h−1 and CH 4 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 CoS x species can provide abundant active sites to increase CO 2 adsorption and meanwhile enhance the absorption spectrum in the visible light region, facilitating the CO 2 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. [ABSTRACT FROM AUTHOR]