Reversible Iodine Capture by Nonporous Adaptive Crystals of a Bipyridine Cage

The ability to capture radioactive iodine species is crucial for nuclear accident preparedness and nuclear waste treatment; however, it remains a challenge. Here we report a new readily obtainable nitrogen-rich nonporous cage (BPy-Cage) based on bipyridine building blocks that supports iodine capture. This cage is able to capture not only volatile iodine in vapor form but also iodine dissolved in various organic solvents or aqueous media with an iodine uptake capacity of up to 3.23 g g^-1. The iodine within the cage (I@BPy-Cage) can be released quickly upon immersing the bound solid form in DMF, allowing for control over acylation reactions. The cage solids reported here could be reused several times without substantial loss in their iodine capture performance. The effectiveness of the present system is ascribed to its ability to support strong iodine-bipyridine nitrogen lone pair interactions.