Acc. Chem. Res. 2007, 40, 1005–1013
Ionothermal Synthesis of Zeolites, Metal–Organic Frameworks, and Inorganic– Organic Hybrids EMILY R. PARNHAM* AND RUSSELL E. MORRIS EaStChem. School of Chemistry, University of St Andrews, Purdie Building, St Andrews KY16 9ST, Scotland, U.K. Received February 4, 2007 ABSTRACT Ionothermal synthesis, the use of ionic liquids as both solvent and template (structure-directing agent), has been used to prepare zeolites and inorganic–organic hybrids such as metal–organic frameworks. The underlying properties of the ionothermal method are discussed, and it is compared with traditional hydrothermal preparative methods. The materials resulting from ionothermal synthesis are described, and any structural features that can be related to the ionic liquid used as the solvent are discussed. Future areas of potential interest are also considered.
Introduction The search for new porous solids remains at the forefront of synthetic materials science as their architectures continue to be of interest for many established and emerging applications.1–3 Until relatively recently, the field of crystalline porous solids was dominated by aluminosilicate zeolites, but since the 1980s, many other fascinating materials have been produced, ranging from aluminophosphates4 to metal–organic frameworks5,6 and other inorganic–organic hybrids.7,8 In general, these materials are made in a so-called solvothermal synthesis, often in sealed autoclaves under autogenous pressure. By far the most common solvent used is water, giving rise to hydrothermal synthesis,9 but many other solvents have been tried.10 This Account details the recent developments in ionothermal synthesis of open framework structures, where the solvent used is predominantly an ionic liquid or eutectic mixture, which also acts, in many cases, as the template provider. In the 1940s, Barrer11 and Milton12 hydrothermally synthesized the first zeolites. Synthetic hydrothermal Emily Parnham was born in Dumfries, Scotland. She received her MSci(Chem) from Durham University (Durham, England) in 2003 and her Ph.D. from the University of St Andrews in 2006. Her research focused on the ionothermal synthesis of zeotype materials. She is currently employed by Johnson Matthey within the technology center. Russell Morris was born in north Wales and graduated in chemistry from the University of Oxford before completing postdoctoral studies at the University of California (Santa Barbara, CA). In 1995, he joined the staff at the University of St Andrews where he is currently Professor of Structural and Materials Chemistry. His interests include new methods for the synthesis of porous materials, including zeolites, aluminophosphates, and inorganic–organic hybrid solids, gas storage materials for medical applications, and dendrimer-based homogeneous catalysts. He is a recent winner of the Royal Society of Chemistry Corday-Morgan medal and the Royal Society of Chemistry Barrer award, both for his work on porous materials. 10.1021/ar700025k CCC: $37.00 Published on Web 06/21/2007
2007 American Chemical Society
zeolite formation involves mixing the reagents, usually the tetrahedral atom source or sources, an organic structuredirecting agent (SDA, often called the template), a mineralizer, and the solvent. The mixture is then heated (
