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

•Catalytic activity of δ-MnO2 was boosted through potassium incorporation for efficient carbonylation of amines by CO2.•δ-MnO2 with different amounts of vacancies of both oxygen and Mn were hydrothermal synthesized by the addition of different amounts of KOH.•The δ-MnO2 catalyst with the optimal molar ratio of KOH to δ-MnO2 of 2.0 displayed the best performance.•Its high activity is attributed to high oxygen vacancies on the surface.