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[Display omitted] • A novel 3DOM Ag 2 S-CoO x /NC had been developed by integrating ultrafine Ag 2 S QDs on the surface of 3DOM CoO x /NC. • The 3DOM Ag 2 S-CoO x /NC composite exhibited remarkable performances for the photocatalytic conversion of CO 2 and H 2 O vapor to fuels. • There were dual Z-scheme charge transfer pathways in the 3DOM Ag 2 S-CoO x /NC. • The key role of Ag 2 S QDs was served as an auxiliary to improve the electronic structure and facilitate adsorption/activation capacity of CO 2 and H 2 O. • The multiple photocatalytic mechanisms of CO 2 reduction were further identified by in situ DRIFTS. Rational design of advanced architectural photocatalysts with efficient separation and transfer of photoinduced charge carriers, and well solar light absorption ability is of critical significance for solar energy utilization and CO 2 -to-fuel conversion. Herein, a novel three-dimensional (3D) ordered hollow-wall hybrid composite (3DOM Ag 2 S-CoO x /NC) has been developed by integrating ultrafine Ag 2 S quantum dots (QDs) on the surface of metal–organic frameworks (MOFs)-derived hierarchically ordered macroporous nitrogen-doped carbon skeletons with implanted CoO x nanoclusters (3DOM CoO x /NC). Compared with pristine 3DOM CoO x /NC and traditional ZIF-67-derived CoO x /NC, the constructed 3DOM Ag 2 S-CoO x /NC composite exhibits remarkable performances toward the photocatalytic conversion of CO 2 and H 2 O vapor without any sacrifice reagents to fuels (CO-66.00 μmol g−1h−1, CH 4 -1.21 μmol g−1h−1 and C 2 H 4 -2.33 μmol g−1h−1) and a higher C 2 H 4 selectivity (16.47%) in the gas–solid system under light irradiation (λ > 420 nm). Impressively, dual Z-scheme charge transfer pathways in the 3DOM Ag 2 S-CoO x /NC can provide good channels for boosting electron transfer and charge separation. Experimental characterizations combined with density functional theory (DFT) calculations further elucidate that the key role of Ag 2 S QDs is served as an auxiliary in the 3DOM Ag 2 S-CoO x /NC catalyst to improve the electronic structure and further facilitate adsorption/activation capacity of CO 2 and H 2 O. Moreover, the multiple photocatalytic mechanisms including related key intermediates and conversion process of CO 2 molecules are further identified by in-situ diffuse reflectance infrared fourier transform spectra (DRIFTS). This innovation provides a novel strategy to design well-designed hierarchically porous hybrid structures for photocatalytic CO 2 reduction to high-value fuels. [ABSTRACT FROM AUTHOR]

[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]