One-dimensional fluorescent covalent organic frameworks rich in exposed sp3-N sites for ultra-fast iodine capture and visual monitoring

Abstract

Up to date, capturing radioactive iodine from nuclear waste remains an important issue in pollution control, especially for highly volatile CH3I and I2. With further research, covalent organic frameworks have shown great potential in iodine capture, and several COFs with high adsorption capacities have been reported. However, improving the capture rate of gaseous iodine remains a major challenge at present. To this end, researchers have improved iodine capture rates by introducing macropores, nitrogen sites, and heteroatoms. Emergingly, 1D COFs are used in the field of catalysis due to their abundant exposed sites. Inspired by this, it is feasible to increase the exposure of N sites to improve the iodine capture rate. Herein, we report a strategy based on 1D COFs (COF-1D6 and COF-1D7) with the introduction of exposed sites, which significantly enhances the adsorption rates of I2 and CH3I, while maintaining a high loading capacity. In particular, COF-1D6 with completely exposed sites exhibited the K80% of 1.07 g·g–1·h–1, far higher than other reported COFs adsorbents. Meanwhile, the excellent fluorescence of COF-1D6 also enabled visual monitoring of the CH3I adsorption process. This work provides new insights into rapid iodine capture from the perspective of exposure sites.