Tailoring pillararene-based receptors for specific metal ion binding: From recognition to supramolecular assembly

Selective binding towards metal ions has gained significant attention due to the roles this phenomenon plays in diverse fields including biological metabolism, hydrometallurgy, environmental issues, material science and management of nuclear fuel. The obtained binding ability depends mainly on the chemical structure of the specific host molecules, which results in guest recognition through certain optical transduction. Pillararenes, a new class of supramolecular hosts, are akin to calixarenes but consist of (O-substituted) hydroquinone units linked together with methylene bridges at the para positions, resulting in a symmetrical pillar-shaped architecture. Due to their unique structure and easy functionalization, these emerging supramolecular macrocycles can be made to display a large array of interesting chemical or physical properties. In this review, we present the progress made so far in applications of pillararene-based receptors for selective binding, recognition and separation of metal ions. Meanwhile, pillararene-based supramolecular systems that have been self-assembled by metal-ligand coordination have also been summarized. (C) 2020 Elsevier B.V. All rights reserved.