Polymorphism molecular history

The first part of the book documents the history, structure, chemistry, formulation and characterizations of zeolites in Chapters 1-4. The past 60 years have seen a progression in molecular sieve materials from aluminosilicate zeolites to micro-porous silica polymorphs, microporous aluminophosphate-based polymorphs, metallosihcate and metallophosphate compositions, octahedral-tetrahedral frameworks, mesoporous molecular sieves and, most recently, hybrid metal organic frameworks (MOFs). 

The history of molecular sieve synthesis encompasses some 40 years and includes the preparation of aluminosilicate zeolites U), phosphorus-substituted aluminosilicates (2 3), and the microporous silica polymorphs (4). More recently, the compositional and... 

By some investigators the transition temperature has been found to vary somewhat according to the previous history of the substance, a behaviour interpreted by Smits as confirming his view (p. 28) that polymorphic forms are equilibrium mixtures of different molecular species. The necessity of making sure that one is dealing with a pure homogeneous solid and not with a mixture of polymorphous forms must also be emphasised (p. 46). 

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