Dr Dewi Lewis
The central theme is the use of computational methods to understand the structure and synthesis of complex materials and to subsequently synthesise new materials with specific properties. Our work covers a range of solids with application as catalysts, sensors and ceramics; the present focus is on microporous materials.
Synthesis of Microporous Materials
Microporous solids, such as zeolites, possess regular channels and cages of molecular dimensions and as a consequence are widely used as catalysts, molecular sieves and ion exchangers. However, their synthesis from a gel medium is difficult to characterise experimentally. We are therefore studying model gels using computational methods to gain insights into the role of the various components in the crystallisation process. A particularly important component are organic amines which act as structure-directing agents; that is they determine which material is formed by acting as a "template". We are trying to understand how this "templating effect" works in order to devise new synthesis routes.1 Furthermore, we are developing new techniques which allow automatic generation of suitable templates,2 opening the way for designer materials.3 Closely coupled to these modelling studies will be a programme of synthesis and characterisation.
Properties of Microporous Materials
The Brønsted acidity of these microporous materials results in their use as catalysts. We are attempting to develop general theories and models to determine structure-property relationships for such sites.4 We are also studying the distribution of extra-framework cations within the micropores in order to characterise their ion-exchange capabilities and their effect on sorption properties. The research projects described (and other) use a wide range of computational methods - QM, forcefield methods, molecular dynamics, Monte Carlo and QSAR. The work involves close collaboration with a number of experimental groups both in the UK and abroad.
- D. W. Lewis, C. M. Freeman, C. R. A. Catlow, 'Predicting The Templating Ability Of Organic Additives For The Synthesis Of Microporous Materials', J. Phys. Chem., 1995, 99, 11194.
- D. W. Lewis, D. J. Willock, C. R. A. Catlow, J. M. Thomas, G. J. Hutchings, 'De Novo Design of Structure-Directing Agents for the Synthesis of Microporous Solids', Nature, 1996, 382, 604.
- D. W. Lewis, G. Sankar, J. Wyles, J. M. Thomas, C. R. A. Catlow, D. J. Willock, 'Synthesis of a Small-Pore Microporous Material Using a Computationally Designed Template', Angew. Chemie, 1997, 36, 2675.
- G. Sastre, D. W. Lewis, C. R. A. Catlow, 'Mechanisms of silicon incorporation in SAPO-5 and SAPO-34', J. Phys. Chem. B, 1997, 101, 5249.
- D. W. Lewis, C. R. A. Catlow, G. Sankar, S. W. Carr, 'Structure Of Iron-Substituted ZSM-5', J. Phys. Chem., 1995, 99, 2377.