A sustainable and green route to furan-2,5-dicarboxylic acid by direct carboxylation of 2-furoic acid and CO2

Abstract Chemical utilization of CO2 via carboxylation has attracted increasing attention in the field of synthesizing carboxylic acids. As the most promising substitute for terephthalic acid, 2,5-furandicarboxylic acid (2,5-FDCA) is a bio-based platform compound with wide application prospects. 2,5-FDCA could be sustainably and economically produced by direct carboxylation of 2-furoic acid (a biomass-derived raw material) and CO2 over Cs2CO3 catalysis. In this paper, the effect of different reaction conditions on 2,5-FDCA yield was investigated, and only generation of 2,5-FDCA without 2,4-FDCA or 2,3-FDCA was determined by HPLC and GC/MS analyses of the resulting product mixtures. Furthermore, density functional theory (DFT) was used to gain deep insight into the mechanism of direct carboxylation reaction. The reaction involved the hydrogen abstraction of furan ring in cesium 2-furoate (FA-Cs) by CO32− and subsequent CO2 electrophilic addition to form C C bond, and the former step was rate-determining for the reaction. More interestingly, the selective formation of 2,5-FDCA relied on molecular features of FA-Cs during the hydrogen abstraction of furan ring.