Mapping the Porous and Chemical Structure-Function Relationships of Trace CH3I Capture by Metal-Organic Frameworks using Machine Learning

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 N-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.

Computational screening and functional tuning of chemically stable metal organic frameworks for I2/CH3I capture in humid environments

High chemical stability is of vital significance in rendering metal organic frameworks (MOFs) as promising adsorbents for capturing leaked radioactive nuclides, under real nuclear industrial conditions with high humidity. In this work, grand canonical Monte Carlo (GCMC) and density functional theory (DFT) methods have been employed to systematically evaluate I2/CH3I capture performances of 21 experimentally confirmed chemically stable MOFs in humid environments. Favorable structural factors and the influence of hydrophilicity for iodine capture were unveiled. Subsequently, the top-performing MIL-53-Al with flexible tunability was functionalized with different functional groups to achieve the better adsorption performance. It has been revealed that the adsorption affinity and pore volume were two major factors altered by the functionalization of polar functional groups, which collectively influenced the iodine adsorption properties. In general, this work has screened the chemically stable high-performance MOF iodine adsorbents and provided comprehensive insights into the key factors affecting I2/CH3I uptake and separation in humid environments.