Adsorption behavior and structural transformation mechanism of ZIF-8 material on iodine vapor with varying particle sizes

Developing effective iodine capture technologies is critical for both nuclear safety and environmental protection. This study investigates the iodine adsorption properties of ZIF-8, a metal–organic framework (MOF). ZIF-8 samples with varying particle sizes (∼50 nm, 90 nm, 150 nm, and 8 μm) were synthesized and tested for iodine vapor adsorption at 80 °C. Iodine uptake continuously increased with time, reaching ~ 3500 mg/g after 24 h without reaching equilibrium, with no significant dependence on particle size. Structural changes in ZIF-8 were observed, as iodine accumulation led to the breakdown of the framework into an amorphous gel-like substance, representing a previously unreported phase transformation. SEM and XRD characterization confirmed the collapse of the crystalline structure after iodine loading. These results indicate that iodine adsorption in ZIF-8 involves strong chemisorption in addition to physical uptake, causing irreversible framework transformations. This work highlights the influence of particle size and provides important insights for using ZIF-8 in effective radioactive iodine capture.