A systematic first-principles study of volatile iodine adsorption onto zeolitic imidazolate frameworks

Zeolitic imidazolate frameworks (ZIFs) are considered promising materials to adsorb volatile iodine due to their large surface areas and high thermal/chemical stability. By using density functional theory (DFT), the volatile iodine I2 and CH3I adsorption onto five different ZIFs (SALEM-2, ZIF-8, ZIF-Cl, ZIF-90 and ZIF-65) were investigated systematically, including interaction mechanisms and the inhibiting effects of potential contaminants. The long-range interactions were found to play an important role in the volatile iodine adsorption. Interestingly, it's found that secondary bonds are all formed after volatile iodine adsorption onto ZIFs. Moreover, except ZIF-65, there is a remarkable charge transfer from considered ZIFs to I2 compared with CH3I. The results of adsorption energies of potential contaminants highlighted that C6H6 has the strongest inhibiting effect towards volatile iodine adsorption onto ZIFs, whereas CO, NO and CH4 have the negligible inhibiting effects. The conclusions could be useful for future design and selection of better adsorbents for capturing radioiodine, but its experimental verification is still an essential work.