Single‐Atom Barium‐Mediated Hydrogen‐Bonding Interaction via Mortise‐and‐Tenon Interlock for Rechargeable Biomass Electrooxidation in Pure Water

ABSTRACT Electrooxidative upgradation of biomass‐derived molecules like 5‐hydroxymethylfurfural (HMF) offers a carbon‐neutral blueprint to produce valuable chemicals, with conversion efficiency highly relying on the strong base and costly membrane use. Herein, we anchor single‐atom Ba into nickel‐oxyhydroxide as the mortise of sulfate (tenon) to construct a rechargeable anode S‐Ba 1 Ni 1‐ x OOH for decoupling HMF electrooxidation, enabling quantitative 2,5‐furandicarboxylic acid (FDCA) production without alkali, potential, and membrane. This decoupling system involves i) active Ni 3+ −O (re)generation via charging and ii) extraction of H atoms of HMF with Ni 3+ −O to undergo deprotonation into FDCA (∼100% conversion and selectivity) in pure water without electricity (discharging). Hydrogen‐bonding interaction between surficial sulfate and hydroxide of HMF can accelerate the substrate migration toward solid–liquid interface with enhanced conversion. Theoretical calculations expound that hydrogen‐bonding interaction decreases the hybridization degree between O‐2p and H‐1s orbitals in O─H bond of HMF to heighten its H removability, thereby fostering complete HMF oxidation into FDCA. Various biomass derivatives are also amenable to this decoupling system, affording >96.3% yields for acids. Techno‐economic analysis illustrates that replacing strong alkali with pure water can reduce the production cost of FDCA by 50.5%, underlining the wide prospect of this decoupling strategy and endowing an attractive route for biomass valorization.