ABSTRACT
The potential of molecular recognition led early on to investigations of supramolecular complexation for the purpose of separation and puriˆcation. Environmental control is a particular challenge for supramolecular chemistry. Many metal ions such as mercury, thallium, chromium, cobalt, and nickel salts as well as anions such as chromates, phosphates, nitrates, and arsenates, are pollutants in wastewater, soil, and industrial emissions. Their toxicity, enhanced by accumulation in living systems, has led to many attempts to eliminate them also by supramolecular complexation. Puriˆcation of industrial and natural products also calls for application of new technologies, which allow the production, for example, of drugs with high purity and the recycling of valuable and potentially toxic compounds. Separations with the help of supramolecular complexation were traditionally aiming at analytical applications;1 corresponding chromatographic methods are dealt with in detail in Chapter 6. Several other separation techniques also rely on selective intermolecular interactions but can only be mentioned here. Metal-organic frameworks (MOFs), which are hybrid porous materials, are presented already in the introduction of this book and can be used, in particular, for gas separation and storage of hydrogen and methane, for example.2 Incorporation of additional functionalities into MOF backbones of zinc oxide and phenylene units leads, for example, to 400% better selectivity for carbon dioxide over carbon monoxide.3
