Imidazole Encapsulation Enabled by Confinement for I₂ and CH₃I Coremoval

Nitrogen-rich small molecules are frequently doped into porous materials to enhance their iodine adsorption properties. To explore how imidazole confinement in metal-organic frameworks (MOFs) affects iodine adsorption, we obtained a UiO-66-based composite by embedding imidazole in UiO-66 pores via solid-phase adsorption (Im@UiO-66). Characterization confirmed that imidazole was successfully confined within the UiO-66 pores, with each unit of UiO-66 accommodating up to 27 imidazole molecules. The density functional theory (DFT) calculations suggested that the octahedral cages of UiO-66 are the primary sites for iodine capture. The adsorption studies revealed that Im@UiO-66 achieved maximum adsorption capacities for I₂ and CH₃I that were 12 and 7.9 times higher than those of UiO-66, respectively, reaching 6.42 g/g for I₂ and 553 mg/g for CH₃I. The spectroscopic analysis indicated that Im@UiO-66 absorbed iodine vapor and methyl iodide via charge-transfer interactions and <i>N</i>-methylation reactions. This study demonstrates that imidazole confinement can effectively enhance the adsorption performance of MOF-based materials, offering valuable insights for the design of iodine adsorbents.