Substitution mechanisms aluminophosphate structures

Later, the synthesis of the family of crystalline silicoaluminophosphate (SAPO- ) was reported. Some of them have structures topologically related to zeolites or AlPOs-n, some having novel structures. SAPO-n composition can be considered in terms of silicon substitution into a hypothetical aluminophosphate framework, the predominant substitution mechanism being silicon substitution for phosphorus. 

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