Facile Construction of Vinyl-Linked Zwitterionic Covalent Organic Frameworks for Efficient Uranium Capture

Extracting uranium from seawater is essential for sustainable nuclear energy but remains a great challenge. Herein, an ionized monomer, PSTMP, which can specifically interact with uranium by strong electrostatic interaction, was incorporated to construct a vinyl-linked zwitterionic covalent organic framework, TFPT-COF-SO3–, via a bottom-up strategy. The vinyl linkage endows TFPT-COF-SO3– with robust structural stability and chemical resistance, while the pendant SO3– groups enable strong electrostatic interaction with UO22+. Benefiting from the high density and uniform distribution of the ionic sites throughout the frameworks, the resulting TFPT-COF-SO3– exhibits a high adsorption capacity (962 mg·g–1) and rapid kinetics (achieving 97% removal from a 10 ppm solution within 35 min) for UO22+ capture. Moreover, it maintains good performance under seawater-relevant conditions, with the UO22+ adsorption capacity of 17.23 mg g–1 in simulated seawater. Mechanism investigations reveal a synergistic electrostatic-coordination and in situ reduction mechanism; the negatively charged –SO3– on TFPT-COF-SO3– offers a strong electrostatic driving force for rapid UO22+ capture, followed by the stable coordination and partial in situ reduction of U (VI) to U (IV). This work demonstrates that the bottom-up strategy for constructing zwitterionic COFs with high charge density represents an effective approach for efficient uranium capture.