Bandgap Engineered Hybrid Covalent Organic Framework Nanofibrous Aerogels Enable Enhanced Photocatalytic Uranium Adsorption

Covalent organic frameworks (COFs) hold great promise for photocatalytic applications, including uranium extraction from seawater (UES). However, the performance of single-component COF is often limited by the rapid recombination of photogenerated electron-hole pairs. To address this challenge, hybrid nanofibrous aerogels (PCNF-A-x) by integrating two photosensitive COFs with complementary bandgap structures and distinct particle and fiber shapes were constructed. This design promotes effective hybridization of COFs at the interface, leading to a minimized charge transfer resistance and an extended charge carrier lifetime of 7.86 ns. The optimized material achieves a remarkable uranium (U) adsorption capacity of 1023.88 mg/g in U-spiked natural seawater with a high removal rate of 99.99% and excellent photocatalytic stability (∼92.16% efficiency retention after 10 cycles). Moreover, it exhibits an attractive U adsorption amount of 8.60 mg/g from natural seawater after 28 days, coupled with exceptional selectivity ( K d = 1.96 × 10 6 mL/g) and robust mechanical properties. This work provides a rational design strategy for high-performance photocatalytic adsorbents and demonstrates their significant potential for UES.