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 & horbar;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 & boxH;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 (approximate to 3.3 ppb of uranium in natural seawater). Notably, the COF-based electrodes delivered an average capacity of approximate to 20.8 mg-U per g for uranyl ion adsorption during 5 days of extraction, approximate to 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. Poly-2,5-dihydroxy-1,4-benzoquinone containing redox carbonyl groups is intercalated into a channel of a covalent organic framework (COF). Under electrochemical modulation, the C & boxH;O groups are transformed into phenol-oxygen anions for rapidly binding of uranyl ions. image