Controllable Active Intermediate in CO2 Hydrogenation Enabling Highly Selective N,N-Dimethylformamide Synthesis via N-Formylation

Abstract

N,N-Dimethylformamide (DMF) is a widely used solvent, and its green and low-carbon synthesis methods are in high demand. Herein, we report a new approach for DMF synthesis using a continuous flow reaction system with a fixed-bed reactor and a ZnO-TiO₂ solid solution catalyst. This catalyst effectively utilizes CO₂, H₂, and dimethylamine (DMA) as feedstocks, demonstrating performance with 99% DMF selectivity and single-pass DMA conversion approaching thermodynamic equilibrium. Moreover, the catalyst demonstrates good stability, with no signs of deactivation over 1000 h of continuous operation. The key to superior activity lies in the synergetic effect of the Zn and Ti sites, which facilitates the formation of active formate species. These species act as crucial intermediates, reacting with DMA to produce DMF. Importantly, the slow hydrogenation kinetics of the formate species prevent the formation of CH₂O* species, thereby suppressing the formation of the undesired byproduct, trimethylamine. This work underscores the potential of kinetically controlling active intermediates in CO₂ hydrogenation to prepare high-value-added chemicals by coupling them to platform molecules. It presents a promising strategy for the efficient utilization of CO₂ resources and offers a valuable solution for large-scale DMF synthesis.