Concepts in the ionothermal synthesis of zeolites and metal organic frameworks

Abstract

Ionothermal synthesis is the use of ionic liquids as the solvent and also as the structure directing agent in the synthesis of materials. The change of solvent chemistry from molecular (as in traditional hydrothermal or solvothermal synthesis) to ionic produces marked effects on the process. This change in chemistry has produced some new concepts that can be used in the synthesis of porous materials. The vanishingly low vapour pressure leads to zeolite synthesis at ambient pressure even at high temperatures, which may have some applications in the manufacture of zeolite coatings. Ionic liquids containing low concentrations of water behave rather differently to other solvents with similar moisture levels. This can lead to lower hydrolysis in the synthesis and to product materials with different chemical compositions to those normally prepared in hydrothermal synthesis. Finally, the properties of ionic liquids are extremely dependent on the nature of the anion present. This adds an extra degree control and can even lead to very unusual effects in zeolite or metal organic framework synthesis, such as the induction of chiral structures in materials comprising only achiral building units.