Analysis of Radioactive Iodine Trapping Mechanism by Zinc-Based Metal-Organic Frameworks with Various N-Containing Carboxylate Ligands

This study aimed to develop effective adsorbents forcapturingradioactive iodine in nuclear power waste gas. Two zinc metal-organicframeworks (Zn-MOFs) were synthesized and found to have favorableproperties such as a large surface area, thermal stability, surfacerich in & pi;-electron-containing nitrogen, and redox potential.Adsorption experiments revealed maximum capacities of 1.25 and 1.96g g(-1) for the MOFs at 75 & DEG;C, with the pseudo-second-orderkinetic model fitting the data well. The Langmuir equation provideda better fit in cyclohexane, with maximum adsorption amounts of 249and 358 mg g(-1) for Zn-MOF-1 and Zn-MOF-2, respectively.The MOFs were also stable during six cycles of adsorption and desorption.Furthermore, electron transfer occurred due to the synergistic adsorptionof Zn, N, and O atoms, resulting in the conversion of some iodineto polyiodide. Zn-MOF-2 exhibited better chemisorption than Zn-MOF-1due to a smaller highest occupied molecular orbital (HOMO)-lowestunoccupied molecular orbital (LUMO) gap. Notably, it was discoveredthat N-containing radicals had stronger interactions with iodine comparedto radicals without N. These findings provide valuable insights intoMOF synthesis and environmental protection.