Study on the performance and mechanism of in-situ introducing secondary ligands to construct efficient CoNi-MOFs photocatalysts for CO2 reduction

This work demonstrates a rational ligand-tuning strategy to enhance the photocatalytic CO 2 reduction performance of bimetallic CoNi-MOFs. By introducing secondary organic ligands (e.g., terephthalic acid, PTA) in situ during the synthesis of the primary DOT-based framework, a series of composite-ligand MOFs were successfully fabricated. Systematic investigation revealed that the type and ratio of the secondary ligand profoundly influence the photocatalytic activity. Notably, the optimized material with a 1:1 DOT/PTA ligand ratio achieved a significant CO yield of 7589.29 μmol g -1 within 5 h, significantly surpassing the performance of the single-ligand counterpart (5059.42 μmol g -1 within 5 h). Characterization results attributed this enhancement to the unique porous spherical morphology of the DOT/PTA (1:1) MOF, which facilitates CO 2 adsorption/activation and exposes abundant active sites. Furthermore, this composite ligand system exhibits superior light-harvesting capability and more efficient separation and migration of photogenerated charge carriers compared to the parent MOF. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis further elucidated that the CO 2 reduction proceeds via a reaction pathway involving the *COOH intermediate. This work offers deep insights into designing efficient MOF photocatalysts through precise ligand engineering. • The composite ligand was introduced into MOFs to enhance the photocatalytic reduction performance of CO 2 . • DOT 1 : PTA 1 composite ligand MOF achieved a CO production of 7589.29 μ mol g -1 . • The CO 2 reduction pathway in a composite ligand MOF was elucidated through the *COOH intermediate.