Effects of different covalent organic frameworks structures on radioactive iodine adsorption

Abstract

As low-carbon sustainable energy source, nuclear energy plays an increasingly important role in human social progress. However, the operation of nuclear power plants has resulted in the emission of volatile radioactive pollutants, including iodine molecules (I₂) and methyl iodide (CH₃I). Radioactive iodine (^129,131I) is harmful to human health and should be removed from the exhaust gas. Covalent organic frameworks (COFs) are a class of emerging organic materials with tunable structures, unique inherent properties and excellent stability, which have great potential as adsorbents for radioactive I₂ capture. This review summarized the common types of bonds, synthesis methods, and specifications of COFs as radioactive I₂ adsorbents. The effect of COF structures on I₂ adsorption were discussed, and the relationships between the inherent characteristics of COF structures and their adsorption performance were analyzed. In addition, the interaction mechanisms of COFs with radioactive I₂ were also discussed. We found that the tunable structures, pore sizes, flexibility, conjugated structure and heteroatoms of COFs have significant effect on the adsorption performance of I₂. Moreover, post-modification and composites with other nanomaterials can improve the adsorption effectively. It is of great significance to design COFs that can be used in practical radioiodine elimination. Finally, we also provide an overview of the challenges in practical applications.