The Structure-Directing Effect In The Synthesis Of Anionic Open-Framework Aluminophosphates

Zeolites and open-framework aluminophosphates are microporous crystalline solids with well-defined pore-structures,which are widely used in catalysis,adsorption,chemical separation,ion-exchange,and host/guest chemistry.In the synthesis of zeolites and open-framework aluminophosphates,the structure-directing agent plays an important role.In the absence of the organic amine,the corresponding open-framework aluminophosphates cannot be obtained.The role played by the organic amine is denoted as the structure-directing effect.It has been demonstrated that the structure-directing effect can be influenced by many synthetic factors.However,the origin of the structure-directing effect and how the structure-directing agent directs the corresponding structure have not been fully understood.In this thesis,we investigated the crystallization process of aluminophosphates with the same open-framework topology in the presence of three different diamines and the structure-directing effect of 1,3-diaminopropane and 1,4-butanediamine in the synthesis of open-framework aluminophosphates.The main results are summarized as follows:1.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 MAS 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.2.The temperature-dependence of the influence of methylene group on the structure-directing effect of 1,3-diaminopropane in the synthesis of open-framework aluminophosphates was investigagted.At 160 °C,aluminophosphates Ui O-18 and APDAB200 were obtained in the presence of 1,3-diaminopropane and 1,4-diaminobutane,respectively.At 190 °C,Ui O-26 and APDAB200,which have the same open-framework topology,were obtained in the presence of 1,3-diaminopropane and 1,4-diaminobutane,respectively.The crystallization processes of the four open-framework aluminophosphates were characterized using XRD and solid-state NMR techniques.It was found that the additional methylene in the 1,4-diaminobutane compared to 1,3-diaminopropane slowed the crystallization of the initial mixture.The non-bonding interactions between the inorganic layers and the structure-directing agents were calculated.The possible starting points of crystallization for these aluminophosphates were analyzed,and the specific fragments required for the formation of each compound were suggested.The study revealed that the structure-directing effect could be influenced by multiple synthetic conditions.