Secondary building units . large pore structures

In addition, in the field of dewaxing (gas oils, HDC residues, lubricating oil, etc.), synthesis of novel molecular sieves with better adsorption and separation abilities is highly desired. In the past 20 years, thanks to the discovery of many molecular sieves with new compositions and structural features [secondary building units (SBUs) and pores], there have appeared a number of new application fields for molecular sieves, such as basic catalysis, extra-large microporous molecular sieve catalysis, redox catalysis, asymmetric catalysis, and dual- and multi-functional catalysis.1-201 All of these will lay a further solid foundation for the development of molecular sieves in catalysis, adsorption, and separation. 

Another way of description of the structures [55] uses, instead of single polyhedra, assemblies of polyhedra (Fig. 2c) that, by translation/rotation in the three directions of space, regenerate the whole framework. These are called secondary building units (SBU) and the concept has been very useful for defining the large pore strategy. 

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