A chemical–electrochemical cascading strategy for the efficient synthesis of 2,5-furandicarboxylic acid and its methyl ester from 2-furoic acid and CO2

Abstract

The electrocatalytic upgrading of biomass-derived furanics offers a sustainable route to high-value monomers for polymer manufacturing. Herein, we report a bromine-mediated electrochemical platform that converts 2-furoic acid and CO₂ into 2,5-furandicarboxylic acid (FDCA) and its dimethyl ester, dimethyl furan-2,5-carboxylate (FDME), under ambient conditions with faradaic efficiency exceeding 80% for the critical debromocarboxylation step. Specifically, our process involves sequential esterification and bromination of 2-furoic acid to yield methyl 5-bromofuran-2-carboxylate (MBFC), followed by electrochemical debromo-carboxylation on Ag to afford 5-(methoxycarbonyl)-2-furoic acid (MFCA). Subsequent hydrolysis or esterification would furnish the synthesis of FDCA and FDME, respectively. Comprehensive mechanistic studies, including in situ infrared spectroscopy, single-crystal facet analysis, and computational investigation, reveal that the key debromocarboxylation reaction proceeds through a two-electron transfer pathway, with Ag (100) and Ag (311) facets exhibiting the lowest activation barriers. Importantly, coupling cathodic debromocarboxylation with anodic bromide oxidation enables a paired electrolysis configuration in which the generated Br₂ can be recycled for substrate bromination, eliminating the need for a sacrificial anode and enhancing electron economy. Such an integrated, redox-balanced system establishes a scalable and environmentally benign route for converting renewable furanics and CO₂ into polymer precursors, highlighting the potential of bromine-mediated paired electrolysis for sustainable electrosynthetic manufacturing.