In–Co–Zn/C–N catalysts derived from ZIFs for selective hydrogenation of CO2 into methanol

Recently, In2O3-based catalysts have shown great promise in methanol synthesis from CO2 hydrogenation due to their high methanol selectivity. However, low CO2 conversion restricts their application. Herein, we report In2O3 combined with zeolitic imidazolate framework (ZIF)-derived Co–Zn/C–N catalysts for the CO2 hydrogenation reaction in a fixed-bed reactor. The catalysts were characterized by X-ray diffractometry, transmission electron microscopy, CO2 and H2 temperature desorption measurements, X-ray photoelectron spectroscopy, and in situ diffuse reflectance infrared Fourier transform spectroscopy. Compared to pure In2O3, In–Co–Zn/C–N-4 (PM) shows higher CO2 conversion, with even higher methanol selectivity. A CO2 conversion of 7.0% was achieved with a methanol selectivity over 77% and the space time yield (STY) of methanol was 3.3 mmol gcat−1 h−1 under the conditions of H2/CO2 = 3 : 1, 2 MPa, 300 °C and GHSV = 6 L gcat−1 h−1. The In–Co–Zn/C–N-4 (IMP) catalyst shows much lower methanol selectivity (46.6%) and stability due to the formation of Co3InC0.75. ZnO effectively weakens the interactions between Co and In, and the physically-mixed method further prevents the formation of Co3InC0.75. DRIFTS results were used to predict the possible methanol and CO production pathway through a formate intermediate for the In–Co–Zn/C–N catalyst.