Thermal-Responsive Conjugated Micropore Polymers for Smart Capture of Volatile Iodine

The capture of radioiodine is crucial for nuclear security and environmental protection due to its volatility and superior environmental fluidity. Herein, we propose a strategy of "temperature-dependent gate" based on a swellable conjugated microporous polymer (SCMP) to significantly improve the capture of volatile iodine. The SCMP is constructed via the Buchwald–Hartwig coupling reaction of building monomers containing amines. It possesses a hierarchical pore structure with restricted pores, which can be "opened" and "closed" by changing the temperature. By virtue of the thermal-responsive pore structure, it reaches adsorption equilibrium for iodine in 2 h with a capacity of 4.3 g g–1 at 90 °C and retains 92.8% adsorbed iodine at room temperature. The SCMP also exhibits a high adsorption capacity up to 3.5 g g–1 for dissolved iodine within 10 min, as well as good radiation resistance and high selectivity for iodine against moisture, VOCs, and HNO3 vapor. The mechanism is clarified for effective iodine capture and caging based on the relationship between temperature and the pore structure. This work develops not only a strategy to enhance the capture of gaseous and dissolved iodine but also a new adsorption mechanism for iodine capture, which can be extended to the separation and caging of resources or volatile pollutants in other fields.