Nanoporous N-Rich Covalent Organic Frameworks with High Specific Surface Area for Efficient Adsorption of Iodine and Methyl Iodide

With the rapid development of the nuclear industry, the effective treatment of radioactive iodine has become an urgent and challenging task. In this article, we synthesized a nanoporous nitrogen-rich covalent organic framework (TTA-DMTP-COF) with a specific surface area of up to 2332 m2/g for the adsorption of iodine (I2) and methyl iodide (CH3I). Adsorption experiments showed that TTA-DMTP-COF exhibited effective I2 and CH3I adsorption properties; the maximum adsorption capacity of I2 is as high as 2.59 g·g–1, and the maximum adsorption capacity of CH3I is 1.60 g·g–1. In addition, TTA-DMTP-COF can effectively adsorb iodine from an iodine–cyclohexane solution, and the adsorption amount is as high as 516.46 mg/g. Mechanistic studies have shown that I2 and CH3I enter the nanopores of COF materials and form charge transfer complexes with various functional groups in TTA-DMTP-COF (including imines, triazine moieties, and residual amino groups). The N-methylation reaction specifically binds CH3I to the nucleophilic N site and generates polyiodides during the adsorption process. Our work demonstrates that TTA-DMTP-COF is an excellent candidate material capable of capturing radioactive iodine from air and solution in harsh environments.