Study of the influence of zinc ion centers on the photo-catalytic CO2 reduction performance and reaction mechanism of ZIF-8 catalysts

Abstract

Herein, a detailed study of ZIF-8 CO₂ photo-reduction catalysts was carried out, focusing on the characterization of the physicochemical properties of the materials, the photo-catalytic performance and the reaction mechanism. Through the systematic characterization of the ZIF-8 catalyst samples, the differences in the crystal structure, morphological features, specific surface area and optical properties of the materials were investigated. In addition, the catalytic mechanism of the catalysts was investigated in detail by in situ DRIFTS and DFT calculations, and the following conclusions were obtained: among the ZIF-8 catalysts prepared with different ratios of metal centers and ligand precursors, ZIF-8 (8-1) has a more obvious crystalline structure, stronger photoelectron transfer ability (τ_avg = 2.47 ns), and larger specific surface area (1180.33 m² g⁻¹), thus possessing the optimal catalytic activity, with a CO generation rate of 1.14 μmol g⁻¹ h⁻¹ and a CH₄ generation rate of 0.62 μmol g⁻¹ h⁻¹, and the selectivity of CH₄ was 35.28%. The band gap width of the material can be controlled by modulating the content of Zn metal ion centers to promote the photogenerated charge transfer during CO₂ adsorption reduction, which corresponds to the enhancement of catalyst activity. The deep-rooted mechanism of CO₂ catalytic reduction was revealed, and *COOH and *CHO as the key rapid-control steps of the CO₂ catalytic reduction reaction; the energy barrier magnitude of the former (1.56 eV) controlled the reaction product yields, while the energy barrier magnitude of the latter (1.06 eV) was the key to regulate the product selectivity.