Materials chemistry: Liquefied molecular holes.

Abstract

Porous solids have many uses in the chemical industry, which has stimulated the development of several generations of such materials. A new generation has now arrived, with the report of permanently porous liquids. See Letter p.216 Materials that are intrinsically porous, consisting of molecules organized in cage-like structures, are generally solid at usable temperatures. A few liquefiable, rigid cavity-containing molecules have been described, but they do not contain permanent pores as liquids inevitably flow to fill any available spaces. Now Nicola Giri et al. have developed a new type of 'porous liquid' consisting of a high concentration of modified cage molecules in a crown ether solvent that combine to generate permanent, unoccupied cavities in the liquid phase. The authors show that this free-flowing liquid can solubilize methane gas more efficiently than non-porous liquids. Porous liquids have potential in applications such as catalysis, extraction, and gas capture or separation.