Novel nitrogen-rich conjugated microporous polymers for efficient capture of iodine and methyl iodide

Abstract

With the global energy crisis stemming from the depletion of fossil fuels, the emergence of nuclear energy has spurred advancement in radioactive element capture technology. Radioactive iodine, found in nuclear waste, poses significant threats to both the environment and public safety. Consequently, the development of efficient radioactive iodine adsorbents has become a critical objective. In this study, we have successfully designed and synthesized three novel nitrogen-rich conjugated microporous polymers (CMPs), i.e., Car-CMP-1, Car-CMP-2 and Car-CMP-3. These CMPs exhibit outstanding iodine vapor capture capacities (4.98, 3.38 and 5.10 g g⁻¹, respectively) at 75 °C under atmospheric pressure, as well as exceptional iodine capture abilities in n-hexane solution. Moreover, the captured iodine can be rapidly released in methanol, showcasing excellent recyclability. The extensive π-conjugated structure and abundant electron-donating nitrogen sites of CMPs contribute to their remarkable iodine capture performance. Additionally, the three CMP materials demonstrate superior capture efficiency for methyl iodide vapor (with adsorption capacities of 1.6 g g⁻¹, 1.1 g g⁻¹ and 1.9 g g⁻¹, respectively) and the mixed vapor of iodine and methyl iodide. FT-IR, UV-vis and Raman spectroscopy analyses reveal the presence of electron donor–acceptor pairs between the CMPs and iodine, indicating the charge-transfer (CT) interactions that confer ultra-high iodine capture capabilities to CMPs.