Synergistic catalysis of mesoporous Cu/Co3O4 and surface oxygen vacancy for CO2 fixation to carbamates

Abstract

As one of the most important defects, oxygen vacancy (OV) on the surface of transition metal oxides can function as catalytic reactive site for various reactions. Herein, Cu-doped Co3O4 (Cu/Co3O4) catalyst with rich surface OV was developed for efficient and quantitative transformations of CO2, primary amines, and propargyl alcohols to oxazolidinones at mild reaction conditions. Both initial formation rate of oxazolidinone and surface acidity on the Cu/Co3O4 increased with its surface OV concentration. The doped Cu species in Cu/Co3O4 functioned as an active site for propargyl alcohol activation, enhanced the surface OV concentration for CO2 activation, and improved the surface acidity to promote the rate-determining step in CO2-to-oxazolidinone transformation. In addition to oxazolidinones, Cu/Co3O4 was applicable to various β-oxopropylcarbamates syntheses by coupling CO2, propargyl alcohols and secondary amines. This research demonstrates a synergistic cooperative catalysis between Cu and surface OV for CO2 transformation to high-valuable N-containing chemicals.