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

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., Co0.1Zn0.9) exhibited higher CH4 selectivity (29.32%), while the high Co ratio (e.g., Co0.9Zn0.1) 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.