Adhesive tape-inspired COF/Polymer crosslinked networks for efficient uranium extraction from seawater

The ocean holds vast reserves of uranium that can sustain the long-term fuel supply for nuclear power. However, current poly(amidoxime) (PAO)-based adsorbents usually suffer from insufficient exposure of active sites. In this study, we report an aerogel network structure composed of covalent organic framework (COF) nanosheets combined with PAO for uranium extraction from seawater. Here, the COF nanosheets not only contribute additional adsorption sites but also function as "adhesive tape" to effectively disperse polymer molecular chains. After further covalent cross-linking/ionic cross-linking, the stability of the aerogel in water is significantly improved. The cross-linked aerogels demonstrate excellent efficacy in removing U(VI), as evidenced by their high adsorption capacities (CP-150: 275 mg/g and CP-Ca: 207 mg/g in 8 ppm spiked simulated seawater) and high removal rates of uranium from various water samples (> 98 %). The adsorption behavior of U(VI) on CP-150/CPCa are in good accordance with the Langmuir adsorption isotherm model and the pseudo-second-order kinetic model. The eta(2) coordination structure of the oxime group with uranyl ion has been verified through extended Xray absorption fine structure (EXAFS) analysis. This work offers new strategies for the construction of novel PAObased adsorbents and highlights the potential application of 2D COFs in uranium extraction from seawater.