Cu–Fe bimetallic MOF enhances the selectivity of photocatalytic CO2 reduction toward CO production†

The rational design of multi-ligand bimetallic MOFs with a monomolecular structure is a very effective way to study product selectivity of the photocatalytic CO₂ reduction reaction (CO₂RR) using MOFs-based catalysts. Herein, a new Cu–Fe bimetallic MOF material, namely Cu-MOF–Fcdc-20% (Fcdc = 1,1′-ferrocenedicarboxylic acid), was constructed by a multi-ligand strategy to improve the selectivity of photocatalytic CO₂ reduction toward CO production. Specifically, the Cu-MOF based on H₃NTB (4,4′,4′′-nitrilotribenzoic acid) and the phen ligand (1,10-phenanthroline) could catalyze CO₂ to CO, but with relatively low selectivity. After the introduction of the Fcdc ligand, the resulting Cu-MOF–Fcdc-20% displayed not only enhanced CO selectivity but also improved efficiency for CO₂RR. Cu-MOF–Fcdc-20% exhibited a higher CO selectivity of 97.07% and a CO yield of 8.61 μmol g⁻¹ h⁻¹, which is about 5.48 times higher than that exhibited by Cu-MOF (1.57 μmol g⁻¹ h⁻¹, 81.35%). In situ FT-IR, EPR, and other experimental characterizations were further performed to investigate the intrinsic mechanism of the photocatalytic CO₂ reduction process. The in situ FT-IR experimental data show that Cu-MOF–Fcdc-20% can effectively accelerate the rate-limiting step , which in turn improves the rate and selectivity of CO₂ conversion to CO. This work demonstrates that the rational design of the Cu–Fe bimetallic MOF structure can effectively improve the catalytic selectivity of the photocatalytic CO₂ reduction reaction, offering a new way of designing highly selective MOF photocatalysts.