Framework Structure of Zeolitic Crystals

With this in view, the acidic strength of zeolites with reference to the stability of their framework and the presence of proton sites in the crystal structure of zeolites can be directly correlated with their intermediate electronegativity. 

Similarly, the Si-O and Al-O bond lengths are also reported to be dependent on -[Si-O-Al]- bond angle. With this in view, it can be opined that an increase in p results in decrease in 6 and hence lowering of the acidic strength. It has been demonstrated [8, 59] that lower the required frequency for stretching the OH bond, the greater would be the acidic strength of zeolites. For an example, it has been 

Zeolites, as minerals of the tectosilicate group, i.e., three dimensional arrays of interconnected Si04 tetrahedra, have basically three different structural variations [8, 15]  

10 Crystal structures of common zeolites a, b Natrolite, c Heulandite and d Chabazite [8] 

Keeping the above structures in view, the natural zeolites have a unique three-dimensional honeycomb structure (Fig. 2.6i), which creates an open and negatively charged framework through which liquid and gases can be exchanged or 

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