Electrosynthesis of Biodegradable Plastic Monomer Dimethyl Furan-2,5-Dicarboxylate from Inedible Hemicellulose Derivatives and CO2.

Inedible hemicellulose-derived furfural (FF) and its derivatives offer an attractive way for the sustainable production of dimethyl furan-2,5-dicarboxylate (Me2-2,5-FDCA), a monomer of the biodegradable poly(ethylene-2,5-furandicarboxylate) (PEF) plastic. Traditional synthesis methods of Me2-2,5-FDCA involve nucleophilic species from furan derivatives, activated by thermal catalysis, undergoing C-C coupling by nucleophilic attack processes, which exhibit harsh reaction conditions, poor atom economy, and low selectivity. Herein, we reported the electrosynthesis of 5-(methoxycarbonyl)furan-2-carboxylic acid (Me-2,5-FDCA) from methyl furoate (Me-FA) and carbon dioxide (CO2), achieving 80% yield, 93% selectivity, and 6.4% Faraday efficiency (FE). Through subsequent acidification and esterification processes, gram-scale Me2-2,5-FDCA was easily obtained from the electrolytic product. Mechanism studies indicated that CO2, rather than furan derivatives, was first activated by the electric energy to form a CO2 radical anion (CO2•-) and then the CO2•- performed C-C coupling with Me-FA by radical addition processes, which was responsible for the high C5 site selectivity. This innovative electrosynthesis route to the monomer of PEF simultaneously features mild reaction conditions and an excellent atomic economy, which has great potential for application and promotes the transition from petroleum-based plastics to biomass-based plastics.