Effects of different covalent organic frameworks structures on radioactive iodine adsorption

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. [Display omitted] •The applications of COFs in adsorbing I2 and CH3I have been fully reviewed.•The influence of COF structures on adsorption performance was analyzed.•The physical and chemical adsorption mechanisms were summarized.•The perspectives of I2 and CH3I adsorption by COFs are discussed.