Cobalt-ion center engineering in ZIF-67 for enhanced photothermal catalytic CO2 reduction: mechanistic insights into intermediate regulation and activity optimization

Abstract

Herein, a detailed study of ZIF-67 CO₂ photothermal reduction catalysts was carried out, including the characterization of their physicochemical properties, photothermal catalytic performances and reaction mechanisms. Through the systematic characterization of ZIF-67 catalyst samples, the differences in their crystal structures, morphological features, specific surface areas and optical properties were investigated. In addition, the catalytic mechanism of the catalysts was investigated in detail by in situ DRIFTS and DFT calculations. The experimental results showed that among the ZIF-67 catalyst prepared with different ratios of Co²⁺ and 2-MI precursors, the ZIF-67 (8–1) catalyst exhibited an distinct crystal lattice structure, strongest photoelectron transfer ability, and largest specific surface area, resulting in an optimal catalytic activity (total yield = 4.71 μmol g⁻¹ h⁻¹). The band gap width of this material could be controlled by regulating the content of Co metal-ion centers to promote the photogenerated charge transfer in the adsorption–reduction process of CO₂, corresponding to an enhancement in its catalytic activity. The mechanism of CO₂ catalytic reduction showed that *COOH and *CHO are the key intermediates in the rate-controlling steps in the CO₂ catalytic reduction reaction, and the energy barrier of the former controlled the reaction product yield, while that of the latter was the key to regulate product selectivity.