Tuning Co–Zn bimetallic synergy in ZIF-67@ZIF-8 catalysts for selective photothermal CO2 reduction: mechanistic insights and performance optimization

Abstract

Herein, Co–Zn bimetallic center-modulated ZIF-67@ZIF-8 composites were prepared by ultrasonic synthesis, and the effects of the metal ratio on the photothermal coupling catalytic CO₂ reduction performance and product selectivity were systematically investigated. The experiments showed that catalysts with higher Zn content (e.g., Co_0.1Zn_0.9) exhibited higher CH₄ selectivity (29.32%), while the high Co ratio (e.g., Co_0.9Zn_0.1) significantly enhanced the CO generation rate (3.13 μmol g⁻¹ h⁻¹). Characterization by N₂ adsorption, XRD, XPS, UV-vis DRS, and in situ DRIFTS revealed that the metal ratio affected the CO₂ adsorption and electron transport efficiency by modulating the catalyst specific surface area (1213 → 555 m² g⁻¹), the band gap width (3.53 → 3.39 eV), and the distribution of the surface-active sites. The DFT calculations further revealed the synergistic effect of Co/Zn: high Zn content lowers the *CHO generation barrier (3.45 eV) and promotes the CH₄ pathway, while the Co center enhances CO₂ activation. This study provides a theoretical and experimental basis for the optimization of CO₂ reduction product selectivity through precise regulation of metal centers.