More than 10% of the world's energy consumption is devoted to purifying chemical mixtures. The development of more energy-efficient processes to separate mixtures thus would significantly reduce carbon emissions and the cost of manufacturing goods. Gaseous mixtures in particular could be separated more energy-efficiently than by e.g. distillation 2 instead via selective adsorption on a solid-state, porous material † . Porous solids composed of porous organic cage molecules have auspiciously demonstrated the ability to separate gases in application to carbon dioxide capture from natural gas and flue gas of coal-fired power plants, xenon/krypton separations, and sulfur hexaflouride capture. Porous cage solids with high adsorptive selectivities may serve as vapor sensors as well. Porous organic cages are molecules that harbor (i) a cavity that is intrinsic to their molecular structure and (ii) windows through which gas molecules can enter the cavity.