Boosting catalytic activity of d-MnO₂ through potassium incorporation for efficient carbonylation of amines by carbon dioxide

The synthesis of N,N'-dialkylurea from carbonylation of amines with CO2 over 8-MnO2 catalyst is a highly attractive green route, however, the catalytic performance of 8-MnO2 is still far from satisfied. Here, we report a new strategy for fine tuning the physicochemical properties of 8-MnO2 through KOH hydrother-mal activation, resulting in superior catalytic performance with N,N'-dialkylurea yield as high as 77.09% using NMP as solvent at 160 ? for 4 h, as compared to only 43.41% for the pristine delta-MnO2. The yield is further boosted to 92.02 % by using PEG 400 as solvent. Systematic analysis based on characterization techniques reveals such superior catalytic performance is closely related to, on the one hand, the potassium-incorporation and catalysis induced modification of the concentration of vacancies of both oxygen and Mn, on the other hand, PEG 400 as solvent is favorable to both absorbance of CO2 and stability of carbamic acids intermediates. (C) 2022 Elsevier Inc. All rights reserved.