Ga-doped Cu/γ-Al2O3 bifunctional interface sites promote the direct hydrogenation of CO2 to DME

The reaction of CO₂ catalytic hydrogenation to dimethyl ether (DME) usually relies on a Cu-containing metal oxide/molecular sieve system; however, the migration of copper species to molecular sieves is unavoidable during the reaction, leading to the loss of Cu⁰ sites and acidic sites. In this work, a Cu/x%Ga-γ-Al₂O₃ bifunctional catalyst was synthesized via the coprecipitation method. Ga was doped into the γ-Al₂O₃ lattice at a low concentration, forming interfacial active sites with surface Cu⁰ species to achieve the hydrogenation of CO₂ to DME. Experimental studies combined with DFT calculations demonstrate that the catalyst remains stable for 180 h and that the Ga-doped Cu/γ-Al₂O₃ interface sites exhibit catalytic effects on CO₂ hydrogenation to CH₃OH and CH₃OH dehydration to produce DME. The doping of Ga increases the specific surface area of the catalyst, reduces the particle size of Cu⁰, enhances the number of acidic and basic sites on the catalyst, and promotes the adsorption of H₂ and CO₂. In addition, a new reaction pathway for DME synthesis was proposed. This work removes the dehydrated component of a traditional Cu-based bifunctional catalyst, enabling two reactions to occur at the same active sites, thus providing a new strategy for the design of novel dimethyl ether synthesis bifunctional catalysts.