Extremely stable amidoxime functionalized covalent organic frameworks for uranium extraction from seawater with high efficiency and selectivity

Uranium extraction from seawater is of strategic significance for nuclear power generation. Amidoxime-based functional adsorbents play indispensable roles in the recovery of seawater uranium with high efficiency. Nevertheless, balancing the adsorption capacity and selectivity is challenging in the presence of complicated interfering ions especially vanadium. Herein, a polyarylether-based covalent organic framework functionalized with open-chain amidoxime (COF-HHTF-AO) was synthesized with remarkable chemical stability and excellent crystallinity. Impressively, the adsorption capacity of COF-HHTF-AO towards uranium in natural seawater reached up to 5.12 mg/g, which is 1.61 times higher than that for vanadium. Detailed computational calculations revealed that the higher selectivity for uranium over vanadium originated from the specific bonding nature and coordination pattern with amidoxime. Combining enhanced adsorption capacity, excellent selectivity and ultrahigh stability, COF-HHTF-AO serves as a promising adsorbent for uranium extraction from the natural seawater.