Silver Modified Covalent Organic Framework Nanotraps for Efficient Radioiodine Capture: Synergizing Charge-Transfer...

Efficient sequestration of radioiodine is imperative for safeguarding ecosystems and advancing sustainable nuclear energy development. Covalent organic frameworks (COFs) are emerging iodine adsorbents, while their practical application is hindered by suboptimal decontamination efficiency under extreme nuclear reprocessing conditions, particularly for ppm-level iodine. For ultra-efficient iodine capture, a tailored linker engineering strategy is developed to precisely control the uniform distribution of silver nanoparticles within a robust sp³-amine-linked COF (Ag⁰-SCU-COF-5). The optimized adsorbent demonstrates a superior dynamic breakthrough capacity of 0.41 g g^-1, achieving 10.8-fold higher than commercial silver-silica gels along with a 4.8-fold improvement over silver-zeolites. Notably, for ppm-level radioactive ¹³¹I₂ vapor, Ag⁰-SCU-COF-5 maintains over 80% decontamination efficiency for 19 h, accumulating an impressive activity of 40 000 Bq (0.134 g ¹³¹I₂/g sorbent). Combined experimental and theoretical analyses elucidate a dual-pathway adsorption mechanism: i) instantaneous iodine trapping through charge-transfer interactions at electron-rich sp³-amine motifs, followed by ii) concurrent redox chemisorption to form AgI, as evidenced by spectroscopic characterization and density functional theory (DFT) calculations.