Highly Selective Purification of Trace ¹³¹ I in Radioactive Wastewater via Adaptive Inflatable Organic Cages with Fully Accessible Sites

As adsorption of radioactive elements in wastewater has drawn growing attention, developing new materials for complex practical radioactive environments is of great importance. In this study, we report two flexibly adaptive cages that serve as a high-performance adsorbent for trace iodine-131 ( 131 I) in off-gas and polluted water such as real nuclear medical radioactive wastewater. Molecular dynamics simulations reveal that the porous cage crystals possess a flexible window that can expand and contract to achieve selective coordination of 131 I in complex water, thus promoting adaptive binding and full utilization of active sites. The cages exhibit a record high iodine uptake capacity of 6.1 g g –1 across a wide pH range and in the presence of a large excess of competing anions, which is 8 times higher than that of the relatively rigid CC3 cage (∼0.8 g g –1 ). Notably, the cages can be used to decrease the total β radioactive activity concentration in actual nuclear medical wastewater containing trace iodine from 1232.97 Bq L –1 to 2.406 Bq L –1, well below the stringent global discharge limit and the US EPA standard of 10 Bq L –1 . This work demonstrates the potential of flexible and inflatable cages for trace 131 I capture in complex radioactive water remediation.