Construction of MOF-on-COF with multifunctional sites for efficient capture and sequestration of radioactive iodine in high-humidity environments

Radioactive iodine has garnered extensive attention due to its severe hazards to human health and the environment. However, the ubiquitous presence of water vapor during iodine vapor capture significantly impairs the adsorption performance. This often leads to reduced activity or even deactivation of adsorbents. To achieve efficient iodine capture and stable immobilization under high-humidity conditions, this study constructed an environmentally friendly MOF-on-COF architecture (Tp-UiO) with multifunctional sites and a three-dimensional framework using the in-situ growth of a metal-organic framework (UiO-66-NH 2 ) on a three-dimensional scaffold of a covalent organic framework (Tp-Azo). Among the samples, the 200Tp-UiO sample exhibited a saturation adsorption capacity of 2585 mg/g under dry static adsorption conditions. This result represented a 261.5% and 55.1% improvement compared to UiO-66-NH 2 and Tp-Azo, respectively. The saturation adsorption capacity reached 2004 mg/g at a relative humidity of 74%, exceeding that of most reported adsorbents. Moreover, after iodine uptake and 7 days of storage, the iodine retention rate remained greater than 95%. A series of detailed characterizations confirmed that the excellent adsorption performance was attributed to the construction of the unique pore structure and the synergistic interactions among multiple functional sites (N − H, N = N, C O, and Zr−O groups). This study elucidated the feasibility of the MOF-on-COF composite structures for radioactive iodine adsorption in high-humidity environments and offered a novel perspective for the field of radioactive iodine capture.