Enhanced high-temperature iodine capture through band-edge control in covalent organic frameworks

The effective capture of radioactive iodine species is crucial in nuclear waste treatment, particularly under high-temperature industrial conditions (≥150 °C), yet it poses a significant challenge. Here, we propose a novel approach for constructing highly efficient iodine traps by precisely controlling band edges in covalent organic frameworks (COFs) through the incorporation of fluorine atoms. This strategy facilitates the transformation of I2 into I5−, thereby enhancing the interactions between the COF host and radioiodine species, leading to a remarkable iodine uptake capacity of up to 2.36 g/g under static adsorption condition at 150 °C, and 36.12 wt% under dynamic adsorption condition at 150 °C. Moreover, the captured iodine can be released by immersing the solid form in DMF solvent, providing a mean to modulate reaction conditions gently. Notably, TFA-COF material can be reused multiple times without significant loss in its iodine capture performance.