Constructing Co and Zn atomic pairs in core-shell Co3S4/NC@ZnS/NC derived from MOF-on-MOF nanostructures for enhanced photocatalytic CO2 reduction to C2H4

Herein, a core-shell structured Co3S4/NC@ZnS/NC heterojunction has been constructed via elaborately synthesizing metal-organic framework (MOF)-on-MOF precursors (ZIF-67@ZIF-8) and following controlled carbonization-sulfidation processes. The developed Co3S4/NC@ZnS/NC achieves higher performances for CO2 photoreduction with water vapor towards CO (28.44 mu mol g(-1) h(-1)), CH4 (1.93 mu mol g(-1) h(-1)) and C2H4 (12.23 mu mol g(-1) h(-1)) in a continuous-flow condition under visible-light irradiation, which are significantly superior than those of Co3S4/NC and ZnS/NC. (CO2)-C-13 isotope tracer analysis verifies that CO, CH4 and C2H4 originate from the carbon source of CO2. Experiments and DFT calculations confirm that constructing an electron transport layer (ZnS/NC) in Co3S4/NC@ZnS/NC can contribute to a feasible channel for the enhanced separation and transfer of charge carriers. In heterojunction, non-bonding Co and Zn atomic pairs as adsorption sites synergistically participate in the CO2 activation through the unique electron transport channel and acquire the lower energy barriers of COOH* formation. Moreover, in situ DRIFTS reveals the key intermediates and possible conversion pathways to main products. This work presents an attractive strategy to construct dual MOFs-derived metal sulfide heterojunctions for high-performance CO2 conversion.