Microporous solids containing silicon and aluminium have many applications, for example, in catalysis, ion exchange and gas separation, and more recently have found uses in electronics, optics and even medicine.  It is no surprise, therefore, that there is keen interest in developing synthetic methods to expand the range of such solids.

Making microporous solids using macrocycles

In their Dalton Transactions Perspective article, Professors Paul Wheatley,Russell Morris and Paul Wright, at the University of St. Andrews, UK, outline recent progress in using oxygen and nitrogen containing macrocyclic molecules in the synthesis of mircoporous solids.  These macrocycles act as 'templates', allowing the inorganic framework of the microporous material to form around them.  This can influence the Si to Al ratio and therefore determine the structure and potential applications of the solid. Macrocycles are particularly useful templates, as they can be prepared in a range of shapes and sizes, and can be used as the free ligand, or complexed via the oxygen or niotrogen atom in the molecule to a metal ion allowing the introduction of a metal into the microporous material. 

There are many potential applications of using macrocyclic molecules in this way, as their use could lead to the production of new types of microporous solids, with useful properties.  The work described by Wheatley and colleagues is focused on oxygen and nitrogen containing macrocycles, but there are further exciting discoveries to be made. 'So far there have been no investigations into the use of phosphorus or sulfur containing macrocycles,' says Wheatley, ' There are interesting possibilities to extend this tyoe of work in these areas and we hope that synthetic chemists will take up the challenge of using such macrocycles to prepare the next generation of microporous materials.'