Nanofiber engineering of covalent organic frameworks via monomer-solvent synergy for high-efficiency uranium capture

Covalent organic frameworks (COFs) show great potential for uranium extraction from seawater and environmental remediation, yet the low utilization of deeply buried active sites remains a critical bottleneck. Here, we first propose a synergistic building-monomer and solvent modulation strategy to successfully fabricate irreversible β‑ketoenamine‑linked COFs with a nanofibrous morphology, which efficiently exposes active sites. The resulting material exhibits a maximum uranium adsorption capacity of 471 mg g^-1 at pH 8.0 and maintains stable performance over at least seven adsorption-desorption cycles. Notably, even under more aggressive pH conditions, its uptake capacity surpasses the highest reported values for similar bulk COFs by 15.4%. In natural seawater, the uranium uptake reaches 10.1 mg g^-1 within 10 days. Mechanistic studies reveal that uranium capture primarily relies on synergistic coordination among the carbonyl groups in the COF backbone and the surface carboxyl/amidoxime groups. This work not only provides a novel approach for morphology control of irreversibly linked COFs, but also opens a new avenue for designing highly efficient adsorbents toward uranium resource recovery and contamination remediation.