Construction of non-fluorine side-chain cation exchange membranes for efficient 5-hydroxymethylfurfural electrocatalytic oxidation

The electrocatalytic oxidation of 5-hydroxymethylfurfural (HMF) represents a promising pathway for producing biomass-derived value-added chemicals. Nevertheless, the use of extremely expensive ion exchange membranes (IEMs) as separators significantly sacrifices the economic benefit in large-scale applications. Herein, we report a cost-effective non-fluorine cation exchange membrane (CEM) by grafting sulfonic acid (-SO 3 - ) groups onto the aromatic side chain of the polyethersulfone (PES) polymer. By tuning the content of –SO 3 - groups, the physicochemical properties of the resulting CEMs can be easily adjusted. Impressively, the optimal HBS-PES-1.0 CEM with fully grafted –SO 3 - groups can achieve a high HMF conversion of 100 %, FDCA selectivity of 98.0 %, and Faradaic efficiency of 98.3 % when used as the separator for electrocatalytic oxidation of HMF, surpassing that of the commercial Nafion 117 membrane (100 % HMF conversion, 98.1 % FDCA selectivity, and 97.4 % Faradaic efficiency). This study provides a cost-effective and high-performance CEM as a substitute for the expensive commercial membrane, paving the way to large-scale commercial applications of biomass upgrading through the electrolysis process.