Direct CO2 Methylation to Value-Added Aromatics Through Tandem Catalysis

The direct CO2 methylation, coupling CO2 hydrogenation with benzene ring methylation, provides a promising strategy to synthesize value-added aromatics using green hydrogen and CO2 as C1 source. The tandem reaction promotes the conversion of CO2 due to the consumption of in situ formed methoxy or methanol over the tandem catalyst of metal oxide and acid zeolite. This review aims to present the thermodynamics advantage and mechanistic insights of direct CO2 methylation process. In practice, catalytic conversion and selectivity for typical tandem catalysts are still far below the thermodynamic equilibrium. The detail roles and proximity effects for metal oxide and acid zeolite are covered in order to give directions to the catalyst design and reaction condition optimization, which has been proposed to overcome the kinetic limitation for the direct CO2 methylation development in future.