Rich oxygen vacancies enhanced the catalytic activities of CO2 with organic amines on CeO2-based catalysts

Abstract

The catalytic carbonylation of amines with CO₂, as an ideal pathway toward carbon neutrality, has garnered significant attention in recent years. In this study, four CeO₂-based catalysts were synthesized and evaluated for the carbonylation of organic amines with CO₂. Among them, N-doped-CM-CeO₂ exhibited the highest performance, achieving a conversion of n-butyl amine of 90.32% and a yield of N,N′-dibutylurea of 90.20%, while maintaining stability over five cycles. Comprehensive characterization, including XRD, BET, Raman spectroscopy, XPS, EPR, and NH₃/CO₂-TPD, revealed that the catalytic activity of the CeO₂-based catalysts is strongly correlated with the concentration of surface oxygen vacancies and acid–base sites. Based on these findings, a reaction mechanism was proposed: CO₂ is adsorbed onto oxygen vacancy sites (Lewis base) on the surface of CeO₂, activating the CO bond, followed by proton transfer and nucleophilic attack, ultimately forming N,N′-dialkylureas via either direct dehydration or through an isocyanate intermediate. This study provides valuable insights into the design of high-performance catalysts for CO₂ utilization.