The Synthesis Of Open-Framework Aluminophosphates And The Structure-directing Effect Of Ethylenediamine

Zeolites and related open-framework materials have been widely used in thechemical industry, catalysis and separation due to the diversity of their structures,pore homogeneity and large specific surface areas. Since the last century, a seriesof new zeolites and open framework materials have been discovered. To achievethe rational design and synthesis of the new microporous crystals with specificstructure and function, understainding the crystallization mechanism and thestructure-directing effect is very necessary. Thus far, no well-acceptedacknowledge on such topic has been developed.In this thesis, we investigated the hydrothermal synthesis ofaluminophosphates in the presence of N-methyl-1,3-diaminopropane orn-propylamine and obtained several new open-framework aluminophosphates. Inaddition, we also investigated the structure-directing effect of ethylenediamine inthe crystallization of open-framework aluminophosphates. The main results aresummarized as follows:1. Heating the same initial mixture with the composition of Al2O3: P2O5:2.0ethylenediamine:226H2O at150C and200C, a two-dimensional (2D) layeredaluminophosphate UiO-15and a three-dimensional (3D) open-frameworkaluminophosphate AlPO4-12were obtained, respectively. Their crystallizationprocesses were characterized by pH, X-ray powder diffraction (XRD), solid-statemagic-angle spinning nuclear magnetic resonance (MAS NMR) and elementalanalyses. By applying the "reverse evolution" analysis to the structure of UiO-15and AlPO4-12, we extreacted their possible onsets of the crystallization (coreunits). The results showed that the heating temperature altered the structure-directing effect of ethylenediamine and the crystallization process of theinitial mixture via changing the structure and chemical properties of thestructure-directing agent of ethylenediamine, the equilibrium of the reactionsoccurring among the source materials, and the assembly of the inorganicoligomers.2. By heating two mixtures with the molar composition of Al2O3:3.0P2O5:4.0ethylenediamine (en):90ethylene glycol (EG):7.9H2O and Al2O3:3.0P2O5:4.0ethylenediamine (en):90H2O at180C, one-dimensional (1D) chain-likealuminophosphate1([AlP2O8H][N2C2H10]) and three-dimensional (3D)open-framework aluminophosphate AlPO4-12([Al3P3O13][N2C2H10]) wereobtained, respectively. Their crystallization processes were investigated usingpowder X-ray diffraction (XRD) and solid-state magic angle spinning nuclearmagnetic resonance (MAS NMR) techniques. The evolution of the coordinationstate of Al and P during the crystallization was monitored. A possible startingpoint (core unit) for the crystallization of both structures was suggested. Thecorrelation between the core units and the long-range ordering of the planes firstappeared in the early stage of both crystallization processes were investigated.The results show that the solvent can affect the structure-directing effect ofethylenediamine by altering the type and distribution of the fragments formed inthe synthetic system and the starting point (core unit) of the crystallization, whichwill determine the structure of the resulting crystals. The long-range orderingalong the direction that is represented by the diffraction peaks which appearedearlier than other diffraction peaks during the crystallization process might beformed from a core unit.3. By heating two mixtures with the molar composition of Al2O3: P2O5:3.0en:226H2O and Al2O3: P2O5:10.0en:226H2O at150C, layeredaluminophosphates UiO-15and UiO-13were obtained, respectively. Theircrystallization processes were investigated using powder X-ray diffraction (XRD) and solid-state magic angle spinning nuclear magnetic resonance (MAS NMR)techniques. The evolution of the coordination state of Al and P during thecrystallization was monitored. During the crystallization of UiO-13, theintermediate phase of UiO-15was observed. The influence of the molarcomposition of the intial mixture on the structure-directing effect ofethylenediamine was investigated.4. In the presence of N-methyl-1,3-diaminopropane, a new microporousaluminophosphate compound [C4N2H14][H2Al3P3O14](2) was synthesized underhydrothermal condition. Single-crystal X-ray diffraction structural analysisshowed that compound2crystallizes in the orthorhombic space group Pbca witha=15.9839(11), b=9.9402(6), c=18.2261(11), V=2895.8(3)3. Itsframework consists of AlO5/AlO6and PO4units forming10-ring channels along[010] direction, where the templates exists. Compound2transformed toAlPO4-25(ATV) upon calcination at550C. It was further characterized bypowder X-ray diffraction(PXRD), inductively coupled plasma(ICP) analysis,scanning electron microscopy (SEM), thermal gravimetric(TG) analysis, andelemental analysis.5. Using n-propylamine as a template, deioned water and secondary-butanol(butan-2-ol) as solvents, a three-dimensional (3D) open-frameworkaluminophosphate [C3NH10][HAl3P3O13](3) and a two-dimensional layeredaluminophosphate [C3NH10]3[Al3P4O16](4) were crystallized from the initialmixtures with compositions of Al2O3:2.4P2O5:5.0n-propylamine:100H2O/butan-2-ol, respectively. They are characterized by X-ray powder diffraction(XRD), thermogravimetric (TG), and elemental (CHN) analyses and structurallydetermined by single-crystal X-ray diffraction analysis. Compound3crystallizesin the monoclinic space group P21/c with a=8.5831(13), b=17.677(3), c=10.4353(12)=123.887(9)°, and V=1314.3(3)3. Compound4crystallizes in the monoclinic space group P21/c with a=11.313(2), b= 14.874(3), c=18.020(6)=125.07(2)°, and V=2481.7(11)3. Theresults show that the properties of solvent have a significant influence on thestructure-directing effect of n-propylamine in the crystallization of theopen-framework aluminophosphates.