Introduction to the Structural Chemistry of Zeolites

Abstract

This chapter provides an introduction to the structure of zeolites and related crystalline microporous materials. The structural characteristics of the zeolite family make it unique among inorganic materials. It is difficult to overemphasize that an appreciation of zeolite structure is critical to an understanding of zeolite properties. We urge you to read this chapter carefully before proceeding to the other chapters of this volume. We will start with a brief introduction to the building units of zeolite materials. We will then show how to build progressively channels and cages out of the primary units. Then we will continue with a discussion of the broad range of compositions that can be found in zeolite materials, with an overview of some important zeolite structures. Because of space, we will focus on the structures that are most likely to be encountered in the laboratory, in the technical literature, and in the marketplace. Following we will show how to use standard reference sources and the associated—and very useful—web resources of structural zeolite information. Because they are frequently found, a very brief discussion of stacking faults in some important faulted zeolite materials follows. We will finish with a rapid survey of the coordination of cations in an important industrial zeolite (zeolite A). A priority throughout the text has been to make relevant connections between structure and properties as frequently as possible. In the writing of this chapter we have assumed that the reader has no previous experience with zeolites. We have also assumed that the reader has some background in general chemistry—what a third-year undergraduate student of chemistry, chemical engineering, materials science, or geology may have—and some familiarity with crystalline materials and elementary crystallographic concepts. We hope that after reading this chapter you will understand how the special properties of zeolites (such as molecular sieving, high adsorption capacity, ion exchange, and so on) are directly related to zeolite structure. You will be familiar with the most common zeolite frameworks and you should be able to understand, in general, the structural descriptions of zeolites as typically found in the technical literature. Finally, you should also be able to use the Atlas of Zeolite Framework Types and the web as starting points to find detailed structural information on any zeolite material.