Chapter 8 - Template-host interaction and template design

Abstract

The synthesis of many, if not most, synthetic microporous and mesoporous materials is facilitated by the use of organic so-called template molecules. The aim of “templating” is to form a material that has specific structural features, which are usually complementary to the structure of the organic template molecule. As such molecules are incorporated into the structure of the solid during synthesis, they have a direct bearing on the structure and concomitant properties of the solid formed. However, the degree to which this “templating effect” is expressed and even the mechanism of the action is often a matter of debate. The parameters that affect product formation are choice of template molecule, temperature, time, pressure, concentration, and agitation. The efficacy of templating or structure-directing action can be simply considered a measure of the closeness of “fit” between the template and the solid structure that is formed. Methods are available that allow the systematic design of new templates. Together, they provide tools that allow chemists to attempt the synthesis of new compositional variants of existing structures or the synthesis of wholly novel materials. New developments, such as automated screening methods, the construction of database systems, and models that allow the inclusion of other key experimental parameters, will further enhance the role of such modeling in the search for new materials. A more significant role for such modeling studies should be in elucidating the exact mechanisms of templating.