The structure-directing effect of organic amines in the multi-template/one-structure phenomenon of microporous crystal synthesis

Abstract

Microporous aluminophosphates with the same open-framework topology were hydrothermally synthesized in the presence of 1,4-butanediamine, 2-methyl-1,5-pentamethylenediamine, and 1,6-hexamethylenediamine. The crystallization processes of such materials were investigated using solid-state NMR in combination with XRD and other techniques. It was found that the crystallization rate of the initial mixture can be significantly affected by the distance between the two N atoms of the diamine. The evolution of the coordination states of the Al and P sites of the open-framework was investigated by using solid-state NMR and 31P {27Al} PT-J-HMQC NMR analyses. The possible starting points of crystallization for these aluminophosphates were analyzed, and the specific fragments required for the formation of each compound were suggested. In combination with the computational simulation, we investigated the role of the diamines in the crystallization of these microporous materials, which is known as the multi-template/one-structure phenomenon.