Cu-induced Ni3 + -O active sites in Prussian blue analogues enable nearly 100 % selective electrooxidation of 5-hydroxymethylfurfural to produce kilogram-scale 2,5-furandicarboxylic acid

2,5-Furandicarboxylic acid (FDCA), a crucial precursor for synthesizing biodegradable polymers as a sustainable alternative to petroleum-derived plastics, has garnered significant interest for its production via electrolysis. However, this approach remains hindered by the inherent weak reactant-catalyst adsorption and sluggish interfacial kinetics. Herein, we report Cu-incorporated NiFe Prussian blue analogues (PBA) that enable rapid electrooxidation of 5-hydroxymethylfurfural (HMF) to FDCA with nearly 100 % conversion, selectivity, and Faradaic efficiency, even at an industrial-scale concentration of 100 mM. In situ Raman and electrochemical characterizations reveal that Cu-incorporation elongates Ni-N bonds and accelerates their reconstruction into defect-rich Ni 2+ -OH species, which undergo deprotonation to form highly active Ni 3+ -O species. X-ray technology and theoretical calculations show that the electronegative Cu 2+ prompts a shift of the d-band center of neighboring Ni atoms toward the Fermi level, thereby enhancing the adsorption of both hydroxyl (-OH) and aldehyde (-CHO) groups in HMF and thus accelerating electrooxidation of HMF to FDCA. Practical applicability using a continuous flow electrolyzer demonstrates the potential for industrial application, achieving a kilogram-scale FDCA production with 99 % purity and a yield exceeding 90 % over 1200 h. This work realizes the valence regulation of active sites in PBA through a cation engineering approach and verifies its feasibility in sustainable biomass electro-oxidation upgrading.