Selective N-Methylation of N-Methylaniline with CO₂ and H₂ over Cu/In₂O₃ Catalyst

N-Methylation of amines with CO2 and H-2 is a potential approach for CO2 utilization because N-methylated amines can be used as solvents and organic intermediates. In2O3-supported Cu (Cu/In2O3) acts as an effective heterogeneous catalyst for N-methylation reaction of N-methylaniline (MA) with CO2 and H-2, showing higher N,N-dimethylaniline (DMA) selectivity than other supported Cu catalysts. On one hand, the dispersion of Cu can be improved by the defective In2O3 support. On the other hand, In2O3 support is active in the dissociative adsorption of CO2 through C-O bond breaking. In addition, the H-2 dissociation ability of In2O3 can also be enhanced by Cu. The combination of Cu and In2O3 is effective in the activation of CO2, the adsorption of intermediate N-methylformanilide (MFA), the hydrogenation of MFA to DMA and the prohibition of C-N bond cleavage side reactions, thereby enhancing the reaction rate of MA conversion and the selectivity to DMA.