Overcoming Chemical Dissociation Processes: Electrochemical Modulation of High‐Affinity Binding Sites for Rapid Uranium Extraction from Seawater.

Currently reported adsorption (hydroxyl or amidoxime) groups must dissociate hydrogen ions to form ─O− units for the coordination with uranyl ions. However, this process suffers a high energy barrier for bond dissociation, leading to the sluggish uptake speed and low adsorption capacity for uranium extraction from natural seawater. Herein, this study proposes a strategy for electrochemical modulation of adsorption sites, which overcomes the chemical dissociation processes of hydrogen ions. Poly‐2,5‐dihydroxy‐1,4‐benzoquinone containing redox carbonyl groups is intercalated into the channels of a covalent organic framework (COF) through in situ cross‐linking of 2,5‐dihydroxy‐1,4‐benzoquinone. Under electrochemical modulation, the C═O groups are transformed into adjacent phenol–oxygen anions to cooperate with the coordination atoms (O and N) on the COF channel for rapid binding of uranyl ions, which gave an absorption rate of 4.2 mg g−1 d−1 (≈3.3 ppb of uranium in natural seawater). Notably, the COF‐based electrodes delivered an average capacity of ≈20.8 mg‐U per g for uranyl ion adsorption during 5 days of extraction, ≈3000 times larger than that of classical tannin‐based adsorbents. The proposed method for preparing electrochemically modulated binding sites is expected to provide guidance for designing high‐efficiency adsorbents in the future. [ABSTRACT FROM AUTHOR]