Rational Design of Cu/Zn Catalysts Supported on Alumina Nanoparticles for CO2 Hydrogenation to Methanol

Converting carbon dioxide (CO2) into methanol (CH3OH) can be a powerful strategy for mitigating emissions and enabling a sustainable methanol economy. This concept relies on sustainable hydrogen production, efficient CO2 capture and highly active and selective hydrogenation catalysts. While traditional Cu/ZnO/Al2O3 (CZA) catalysts are widely used, they often suffer from poor long-term stability due to metal sintering and unclear active site roles at the Cu/Zn interface. This work addresses these challenges by developing highly engineered catalytic materials based on the anchoring of isolated Cu and Zn centers onto the surface of alumina nanoparticles (NPs). The synthesis strategy utilizes alumina NPs surface-modified with silane functionalizing agents containing amino, carboxyl, or thiol terminal groups. These groups promote the specific coordination of Cu(II) and Zn(II) sites, which are subsequently activated under reducing conditions to maximize metal dispersion. A comprehensive characterization suite was employed to validate the material design: TGA, FTIR, and CHNS confirmed surface functionalization, while ICP-OES, XRF, and TEM-EDS verified the anchoring of metal centers. Furthermore, UV-DRS, XRD, DRIFTS, electron spin resonance (ESR), and probe-molecule FTIR spectroscopy were used to monitor the reduction steps and the evolution of the metal oxidation states and coordination environments. Preliminary catalytic tests performed at 30 bar and 250°C demonstrated significant efficiency and selectivity. The results highlight that rational material design, specifically the control of local coordination and metal-support interactions, is a decisive factor in governing catalytic performance for CO2 conversion.