Self-Assembled Pd(II) Nano-Adsorbents for Iodine and Methyl Iodide Capture in Vapor and Aqueous Phases

The excessive release of iodine from industrial and medical activities has led to severe contamination of air and water, causing major concern to public health. Effective capture and secure storage of radioactive iodine in both vapor and aqueous phases are crucial for nuclear safety and ecological protection. In this study, it is explore four non-porous metal-organic coordination cages (MC1-MC4) comprising of Pd-acceptors and diverse aromatic ligands for iodine adsorption across different media. These cages exhibit remarkable iodine uptake, reaching 3.38 g g⁻¹ in the vapor phase at 75 °C and ≈2.73 g g⁻¹ in aqueous solution, with significantly faster adsorption kinetics than covalent organic framework (COF)- and metal-organic framework (MOF)-based materials. Moreover, high adsorption capacities are observed in dynamic flow-through experiments, with MC2 achieving an elution volume of up to 7.8 L g⁻¹ in a 0.5 mM I₃⁻ solution. Practical tests confirm their efficiency in removing iodine from seawater and drinking water, reducing 5 ppm concentrations to ppb levels. Additionally, the cages exhibit outstanding adsorption of methyl iodide vapor, achieving uptake capacities as high as 0.94 g g⁻¹ under ambient conditions. With high stability, recyclability, and scalable synthesis, these metal-organic cages emerge as promising nano-adsorbents for iodine and methyl iodide removal from various environmental matrices.