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 2 @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.
The use of molecular crystalline materials for the separation and purification of chemical raw materials, particularly polar compounds with similar physical and chemical properties, represents an ongoing challenge. This is particularly true for volatile feedstocks that form binary azeotropes. Here we report a new cavity-extended version of calix[4]pyrrole (C4P) that readily forms nonporous adaptive crystals (NACs). These C4P-based NACs allow pyridine to be separated from toluene/pyridine mixtures with nearly 100% purity, as well as the removal of 1,4-dioxane from 1,4-dioxane/water mixtures with high adsorption capacity. Removal of the polar guest (pyridine or 1,4-dioxane) from the guest-loaded NACs by heating under vacuum produces the guest-free crystalline form. In the case of both guests, the C4P material could be reused as demonstrated through 10 uptake and release cycles without apparent performance loss.
The toxicity, corrosiveness, and volatility of elemental bromine presents challenges for its safe storage and transportation. Purification from other halogens is also difficult. Here, we report an easy-to-prepare calix[4]pyrrole-based azobridged porous organic polymer (C4P-POP) that supports efficient bromine capture. C4P-POP was found to capture bromine as a vapor and from a cyclohexane source phase with maximum uptake capacities of 3.6 and 3.4 g•g −1 , respectively. Flow-through adsorption experiments revealed that C4P-POP removes 80% of the bromine from a 4.0 mM cyclohexane solution at a flow rate of 45 mL•h −1 . C4P-POP also allowed the selective capture of bromine from a 1:1 mixture of bromine and iodine in cyclohexane.
The design and synthesis of novel macrocyclic host molecules continues to attract attention because such species play important roles in supramolecular chemistry. However, the discovery of new classes of macrocycles presents a considerable challenge due to the need to embody by design effective molecular recognition features, as well as ideally the development of synthetic routes that permit further functionalization. In 2010, we reported a new class of macrocyclic hosts: a set of tetracationic imidazolium macrocycles, which we termed “Texas-sized” molecular boxes (TxSBs) in homage to Stoddart’s classic “blue box” (CBPQT4+). Compared with the rigid blue box, the first generation TxSB displayed considerably greater conformational flexibility and a relatively large central cavity, making it a good host for a variety of electron-rich guests. In this review, we provide a comprehensive summary of TxSB chemistry, detailing our recent progress in the area of anion-responsive supramolecular self-assembly and applications of the underlying chemistry to water purification, information storage, and controlled drug release. Our objective is to provide not only a review of the fundamental findings, but also to outline future research directions where TxSBs and their constructs may have a role to play.
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