Guest-induced porous gating of a fluorescent nonporous adaptive crystal for efficient radioactive iodine sorption

Nonporous adaptive crystals (NACs) are a new class of organic adsorbents that benefit from the ability of their crystalline structures to adaptively transform in response to specific guest molecules. Herein, a NAC with guest-induced porous gating property is demonstrated within a small organic molecule, BiPyBz. It produces two distinct crystals, the dense packing Cry_Rod and the pore-gating Cry_Quad, in which the pores are opened by water. Remarkably, both Cry_Rod and Cry_Quad can be used as adsorbents for gaseous iodine, with the latter demonstrating the highest uptake capacity of 3.1 g g^-1 at 75 °C among all existing NACs constructed from small organic molecules. The superior iodine adsorption capacity is attributed to the synergistic effect of iodine loaded in gated pores and neighboring layers in the formed crystal. This study underscores the potential of small organic molecules as NACs for the effective adsorption and storage of guest molecules with promising real-world applications.