- © The Mineralogical Society Of America
Microporous crystalline compounds have attracted considerable attention because of their applications in various areas of technology, including catalysis, radioactive waste management, gas separation, adsorption, ion-exchange, etc. Until recently, the major part of research in this field was focused on zeolites and related materials based upon open three-dimensional (3D) frameworks of linked tetrahedra. However, within the last 10–15 years, the quest for new microporous materials led researchers to explore other possibilities, e.g., framework materials containing non-tetrahedral cations that play a crucial role in a framework construction. As for zeolites, this research direction renewed interest in mineral phases as materials formed in the beautiful laboratories of Nature.
The shift of interest from zeolites to materials with non-tetrahedral cations opened a wide range of new possibilities for synthesis and exploration. The chemical range of possible compositions was significantly extended and, from the structural point of view, this chemical extension resulted in endless topological opportunities of framework construction and almost every issue of a journal that deals with structures of minerals and inorganic materials provides new information on framework structures. In this situation, there is a critical need of structure description and classification, from both chemical and topological viewpoints.
The aim of this chapter is to provide a review of possible approaches that can be used for topological and geometrical analysis of microporous structures. For obvious reasons, we do not consider zeolites and related tetrahedral materials here; their detailed topological descriptions can be found in (Smith 1988, 2000; Baerlocher et al. 2001). Most attention will be focused on octahedral-tetrahedral frameworks as important for both mineralogy and material sciences.
BASIC CONCEPTS AND TOOLS
Nodal description of complex structural architectures
Complex structures of inorganic compounds are usually interpreted in terms of coordination polyhedra of cations, i.e., polyhedra centered by cations with anions at their vertices. The most common coordination polyhedra are tetrahedra and octahedra. …