Ionic liquid modified MOF-808 for efficient adsorption and stable capture of radioactive iodine

Radioactive iodine (I₂) is a potential risk to environmental safety and human health. The design of efficient and stable functional materials for I₂ capture remains a challenge. In this work, a simple in-situ impregnation method is used to load Ionic Liquid (IL)-[C₂mim][Tf₂N] into the pores of MOF-808, named IL@MOF. IL@MOF exhibit excellent I₂ removal performance (2.61 g/g), which is 1.75 and 21.75 times higher than that of MOF-808 and [C₂mim][Tf₂N], respectively. This is attributed to the excellent pore structure of MOF-808 and the abundant heteroatom adsorption sites of IL. After modification with hydrophobic IL, IL@MOF exhibit good adsorption performance in high humidity environment. I₂ is retained within IL@MOF in the forms of I₃^- (85 %) and I₂ (15 %). The formation of I₃^- is attributed to charge transfer between the unsaturated site, the heteroatom (N, O, S, F) adsorption site and I₂ within IL@MOF. In addition, the adsorption sites on the IL@MOF surface and adsorption energy are investigated by Density Functional Theory (DFT). Finally, this study provides ideas and guidance for designing MOF-based composites for the effective immobilization of radioiodine.