Defect Engineering Activates Pyrene-Based Covalent Organic Frameworks for Efficient Photocatalytic Uranium Capture

Efficient uranium capture from wastewater is essential for environmental remediation and sustainable nuclear energy, yet current adsorption and photocatalytic approaches remain limited by insufficient active sites, charge recombination, and hydrophobicity. Herein, a defect-engineered pyrene-based covalent organic framework (TP-PYTO-SA) is reported, synthesized from 2,4,6-triformylphloroglucinol (TP) and 2,7-diaminopyrene-4,5,9,10-tetraone (PYTO) with strategic salicylaldehyde (SA) incorporation. The introduced phenolic hydroxyl groups of SA improve hydrophilicity and offer additional uranyl binding sites, while rational defect density optimization (20%) generates localized electron traps. Concurrently, the electron-donating effect of phenolic hydroxyl groups establishes a built-in electric field, which significantly facilitates charge separation and enables a precisely tailored bandgap of 1.70 eV. Under standard AM 1.5G solar irradiation, TP-PYTO-SA₂₀ enables outstanding photocatalytic uranium extraction without a sacrificial agent, achieving an impressive uranium adsorption capacity of 1151.65 mg g^-1, 38.82% higher than pristine TP-PYTO. It demonstrates excellent recyclability (> 90% efficiency retention after 10 cycles) and maintains 95.47% uranium removal in competing-ion-containing simulated wastewater. This work highlights defect engineering via tailored monomer substitution as a versatile paradigm for designing advanced covalent organic frameworks (COFs) for photocatalytic applications in radioactive pollution control and resource recovery.