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.