Design and syntheses of nano-structured ionic crystals with selective sorption properties

This review describes the design and syntheses of nano-structured ionic crystals with selective sorption properties. The complexation of Keggin-type polyoxometalates of [α-XW12O40]n− (n = 3–6) with a macrocation of [Cr3O(OOCH)6(H2O)3]+ and alkali metal ions forms ionic crystals with hydrophilic channels. The ionic crystals can recognize small polar molecules such as alcohols, nitriles, and esters by the difference of one methylene chain. On the other hand, the use of a macrocation of [Cr3O(OOCC2H5)6(H2O)3]+ forms both hydrophilic and hydrophobic channels in the ionic crystals, and the channel-selective sorption and collection of hydrophilic and hydrophobic molecules has been successfully carried out.