Designing self-adaptative cyclized polyacrylonitrile-polyethyleneimine conjugates enhance uranium extraction from natural seawater

Uranium extraction from seawater offers a promising route to secure sustainable nuclear fuel and mitigate environmental issues from fossil fuel consumption, yet it remains hindered by low extraction efficiency and severe biofouling. Herein, we report a self-adaptative adsorbent-cyclized polyacrylonitrile-polyethyleneimine (CPAP)-which undergoes conformation expansion in alkaline seawater to enhance uranium uptake and contracts in acidic solution to facilitate uranium desorption. CPAP exhibits a high adsorption capacity of 22.3 mg g^-1, outperforming all reported fiber-based adsorbents. Its excellent photothermal effect combined with quaternary ammonium functionalities effectively suppresses biological adhesion. Mechanistic studies reveal that electrostatic repulsion and hydrogen bonding drive pH-responsive structural transitions. Furthermore, a self-designed flow-type extraction device demonstrates high uranium extraction efficiency (1.91 mg g^-1d^-1) and excellent cycling stability, underscoring the practical scalability of this strategy. Overall, This work introduces a self-adaptative concept materials for enhancing seawater uranium harvesting, opening the door to fundamental research on designing intelligent adsorbent.