Surface conversion of CuO–ZnO to ZIF-8 to enhance CO₂ adsorption for CO₂ hydrogenation to methanol

The catalytic conversion of CO2 into value-added fuels is a promising strategy for mitigating energy crisis. Cu/ZnO is extensively used for CO2 hydrogenation to methanol (CH3OH) but still generally suffers from low conversion and selectivity. To enhance the conversion and selectivity, novel floral CuO–ZnO@ZIF-8 catalysts were prepared to form diamond-shaped particles ZIF-8 with abundant oxygen vacancies and CO2 adsorption capacity on the surface of floral hydrothermal CuO–ZnO. The oxygen vacancies can provide sites for H* adspecies and CO2 adsorption, which activate the reaction intermediate and reduce the whole energy barrier, thus enhancing the selectivity of CO2 hydrogenation to CH3OH. Moreover, because of the high porosity and high CO2 adsorption capacity of ZIF-8 together with coordination between CuO–ZnO, the adsorption and activation of CO2 over CuO–ZnO@ZIF-8 can be simultaneously enhanced. Among co-precipitated CuO–ZnO, hydrothermal CuO–ZnO, and CuO–ZnO@ZIF-8 (1 : 2, 1 : 4, 1 : 6) catalysts, CuO–ZnO@ZIF-8 (1 : 4) exhibits the best catalytic performance (CO2 conversion 14.64% and CH3OH selectivity 93.41%). This study provides a promising for combining metal–organic frameworks (MOFs) with metal catalysts in CO2 hydrogenation to CH3OH.