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　(-SO3-)　groups　onto　the　aromatic　side　chain　of　the　polyethersulfone　(PES)　polymer.　By　tuning　the　content　of　–SO3-　groups,　the　physicochemical　properties　of　the　resulting　CEMs　can　be　easily　adjusted.　Impressively,　the　optimal　HBS-PES-1.0　CEM　with　fully　grafted　–SO3-　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.　©　2024