Engineering Tandem Catalysis for Direct CO2-Enabled N-Methylaniline Synthesis With a Fixed-Bed Flow Reaction Process.

Integrated tandem catalysis within a continuous fixed-bed reactor represents a promising yet underexplored strategy for process intensification in advanced amine synthesis via CO2 utilization. Here, we demonstrate the direct conversion of nitrobenzene and CO2 with H2 into N-methylaniline in a continuous fixed-bed reactor over a CuZnZrOx catalyst, achieving 99% conversion and 95% selectivity with stable operation exceeding 100 h. Mechanistic studies identify Cu-ZnO interfaces in the form of Cu+-Ov-Zn2-δ serve as active sites for CO2 hydrogenation to key intermediate formaldehyde (CH2O*), which couples the CO2 hydrogenation and methylation of aniline derived from nitrobenzene hydrogenation in kinetics. The tandem configuration provides intrinsic heat-management benefits, recovering 0.341 kg of steam (1.5 MPa, 201°C) per mole of nitrobenzene-far superior to the methanol consumption characteristic of the conventional three-step route. This work highlights tandem catalysis as an effective reactor-level strategy that bridges atomic-scale active-site engineering with kinetic synergies, advancing continuous-flow CO2 valorization toward higher-value amines.