Tuning the Porosity, Solubility, and Gas-Storage Properties of Cuboctahedral Coordination Cages via Amide or Ester Functionalization

The molecular nature of porous coordination cages can endow these materials with significant advantages as compared to extended network solids. Chiefly among these is their solubility in volatile solvents, which can be leveraged in the synthesis, characterization, modification, and utilization of these adsorbents. Although cuboctahedral, paddlewheel-based coordination cages have shown some of the highest surface areas for coordination cages, they often have limited solubility. Here, we show that amide and ester functionalization, which has been widely utilized in porous solids to tune material properties, can be used to tune the solubility, porosity, and bulk adsorbent properties of copper-, chromium-, and molybdenum-based cuboctahedral coordination cages. In addition, we demonstrate that the solubility of a set of diphenylamide-functionalized cages can be utilized to increase their bulk densities for gas storage applications. For a subset of these cages, we further show that amide and ester functional groups can be added postsynthetically, a strategy that is particularly important for the latter where direct cage syntheses with these groups are challenging.