Selective Recognition and Extraction of Short-Chain Perfluoroalkyl Carboxylates by a Supramolecular Receptor.

A supramolecular receptor for short-chain perfluoroalkyl carboxylates was developed. The receptor displays a cage-like geometry, with a defined binding site for the carboxylate head groups and an opening for the perfluoroalkyl side chains. The anionic guests are bound via multiple CH···O hydrogen bonds, as revealed by the crystallographic analysis of an adduct between the receptor and trifluoroacetate. The receptor can be used for the selective extraction of perfluoroalkyl carboxylates from buffered aqueous solutions containing fluoride, chloride, nitrate, carbonate, acetate, and phosphate.