Abstract: In this study, a Ni-Fe metal-organic framework modified by -NH₂ and -SH was synthesized using a simple hydrothermal process for enhancing photocatalytic CO₂ reduction. As expected, the N2S-NiFe (NH₂-BDC/H₄DSBDC, 2:1) displayed excellent photocatalytic CO₂ reduction activity and high CO selectivity (12,412.23 μmol g^-1 h^-1) under visible light irradiation (λ ≥ 420 nm), which is 5 times that of NiFe-MOF. Notably, the excellent photocatalytic performance of N2S-NiFe can benefit from the rich defect trap site caused by the introduction of amino and sulfhydryl groups, accelerating charge transfer and promoting space charge separation, as supported by the photo-electrochemical properties. To better understand the CO₂ adsorption mechanism, density functional theory calculations were performed, which revealed that the Niov site has more negative adsorption energy compared with the Feov site. This study provides a simple strategy to establish efficient photocatalysts for CO₂ reduction through the modification of organic ligands.

Key words: NiFe-MOF, CO₂ reduction, Defect structure, Photocatalytic