Molecular engineering of microporous crystals: (VI) Structure-directing effect in the crystallization process of layered aluminophosphates

The products of piperazine-directed synthesis of two-dimensional (2D) aluminophosphates, AP2pip and AlPO-CJ9, that were crystallized under different conditions for different periods of time were freeze-dried and characterized using XRD and NMR techniques. The core units of the layered aluminophosphates including AP2pip, AlPO-CJ9, and L-DAP, which was hydrothermally synthesized in the presence of racemic 1,2-diaminopropane, were obtained by applying a “reverse evolution” process to their structures. The factors affecting the structure-directing ability of piperazine under acidic and basic conditions were analyzed. The cooperative role of water in directing the layered aluminophosphate of AP2pip under acidic conditions is discussed. After a thorough analysis of the core units of AlPO-CJ9 and L-DAP, a new phenomenon of a “topological-structure-directing effect” or a “topological-templating effect” was observed. The observation of the new phenomenon of a topological-structure-directing effect or a topological-templating effect may contribute to a deeper understanding of the nature or origin of the “structure-directing or templating effect”.

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► The nature of structure-directing ability of piperazine was investigated.
► The crystallization process of two layered aluminophosphates was investigated.
► The factors affecting the structure-directing ability of piperazine were studied.
► The cooperative structure-directing role of water was investigated.
► A new “topological-structure-directing-effect” phenomenon was observed.