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 Co 3 S 4 /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 Co 3 S 4 /NC@ZnS/NC achieves higher performances for CO 2 photoreduction with water vapor towards CO (28.44 μmol g −1 h −1 ), CH 4 (1.93 μmol g −1 h −1 ) and C 2 H 4 (12.23 μmol g −1 h −1 ) in a continuous-flow condition under visible-light irradiation, which are significantly superior than those of Co 3 S 4 /NC and ZnS/NC. 13 CO 2 isotope tracer analysis verifies that CO, CH 4 and C 2 H 4 originate from the carbon source of CO 2 . Experiments and DFT calculations confirm that constructing an electron transport layer (ZnS/NC) in Co 3 S 4 /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 CO 2 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 CO 2 conversion.