A Charged Coordination Cage-Based Porous Salt

Metal–organic frameworks and porous coordination cages have shown incredible promise as a result of their high tunability. However, syntheses pursuing precisely targeted mixed functionalities, such as multiple ligand types or mixed-metal compositions are often serendipitous, require postsynthetic modification strategies, or are based on complex ligand design. Herein, we present a new method for the controlled synthesis of mixed functionality metal–organic materials via the preparation of porous salts. More specifically, the combination of porous ionic molecules of opposite charge affords framework-like materials where the ratio between cationic cage and anionic cage is potentially tunable. The resulting doubly porous salt displays the spectroscopic signatures of the parent cages with increased gas uptake capacities as compared to starting materials. This approach will be widely applicable to all families of porous ions and represents a new and powerful method for the synthesis of porous solids with tailored functionalities.