Sulfate recognition by persistent crystalline capsules with rigidified hydrogen-bonding cavities

Abstract

Locked up: The sulfate anion is selectively encapsulated into rigid hydrogen-bonded capsules upon crystallization of a simple and flexible urea-functionalized ligand in the presence of Mg2+ ions and water (see structure; sulfate: space-filling).The resulting framework persists in the presence of different-shaped anions, allowing the shape selectivity of hydrogen-bonding hosts to be evaluated, and providing a simple way to separate the environmentally relevant sulfate from highly competitive mixtures of aqueous anions. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.