A series of monometal Ni-BTC and bimetallic Co/Ni-BTC-x were prepared for photocatalytic CO₂ reduction. Among these catalysts, the coral-like Co/Ni-BTC-2 catalyst has the highest catalytic activity, with a maximum CO generation rate of 7.392 mmol/g/h due to the low bandgap values and fast charge transfer rates.

Abstract

The photocatalytic reduction of CO₂ using solar energy presents an effective strategy for CO₂ mitigation and utilization. Metal–organic frameworks (MOFs), known for their exceptional CO₂ adsorption capacities and unique structural features, are emerging as novel photoactive materials for CO₂ reduction. In this study, rod-like, reticular, and ball-like Ni-BTC were synthesized using Ni²⁺ ions and 1,3,5-benzenetricarboxylic acid (H₃BTC). Among these, the rod-like Ni-BTC exhibited the narrowest optical band gaps and achieved an outstanding CO generation rate of 4.707 mmol/g/h. To further enhance the photocatalytic performance, Co²⁺ was partially substituted for Ni²⁺ in the rod-like Ni-BTC, resulting in the construction of bimetallic coral-like Co/Ni-BTC-x (x = 1, 2, 3). The incorporation of Co²⁺ facilitated the transformation of the larger rod-like Ni-BTC particles into a coral-like morphology with micro- and nanoscale dimensions. Compared to monometallic rod-like Ni-BTC, the bimetallic catalysts exhibited lower bandgap values, faster charge transfer rates, and superior photocatalytic CO₂ reduction activity. Notably, Co/Ni-BTC-2 achieved the highest CO generation rate of 7.392 mmol/g/h. This study demonstrates that the combination of morphological control and bimetallic approach is an effective strategy for enhancing the performance of MOF catalysts in the photochemical reduction of CO₂.