Synthesis And Structural Characterization Of Aluminum Phosphate Framework Materials In Protic Ionic Liquids

As an important kind of molecular sieve, aluminum phosphate materialshave potential use in catalysis, adsorption and separation. And design andsynthesis of aluminum phosphate materials with novel structures are veryimportant. So far, most of aluminum phosphate materials were achieved in thepresence of organic amines by using hydro/solvothermal method, and it wasfound that the solvents and organic amines are crucial to obtain the aluminiumphosphates with novel structures.Ionothermal synthesis, using ionic liquids as solvent and template, showsthe potential value in the synthesis of new inorganic porous materials. Proticionic liquids (PILs) are a subset of ionic liquids, and are formed through protontransfer from a Br nsted acid to a Br nsted base. Compared to traditional ionicliquids, these ionic liquids are generally lower cost and can be easily prepared inhigh purity.Herein, five protic ionic liquids(PILs) were respectively synthesized byneutralization reaction between acetic acid and organic amines. Then theseprotic ionic liquids were used as solvent and template, a series of synthesis ofaluminum phosphates were carried out in these systems. As a result, tenaluminum phosphates were successfully synthesized in protic ionic liquids bychanging synthetic conditions. Their crystal structures were determined bysingle crystal diffraction data, and powder XRD, NMR, TG-DSC, SEM andCHN elemental analysis were also used to characterize these samples. The maincontents and conclusions are as follows. 1. From the PIL (HDMAPA)(Ac), two aluminiumphosphates,AlPO-PIL1andAlPO-PIL2, have been obtained in the absence and presence ofHF in initial mixture, respectively. HF seems to be important in determining thephase selectivity of the reaction. Without HF, AlPO-PIL1was synthesized,which has one-dimensional chain structure with4-membered rings. On additionof HF to the reaction mixture, a novel layered aluminiumphosphate, AlPO-PIL2was obtained. The organic species in AlPO-PIL2are the protonatedN,N’-dimethyl-1,3-propanediamine (DMPDA) instead of the original ionicliquid, the protonated3-dimethylaminopropylamine (DMAPA). DMPDA can bein situ generated from the protonated DMAPA through intramolecular methylmigration during the crystallization.2. AlPO-PIL3and AlPO-PIL4have been synthesized by using(HDEAPA)(Ac) as the template and solvent. Crystal structure analysis showedthat the organic species in AlPO-PIL3are the protonatedN,N’-diethyl-1,3-propanediamine (DEPDA) instead of the original ionic liquid,the protonated3-diethylaminopropylamine (DEAPA). DEAPA can take place ofintramolecular ethyl migration to generate DEAPDA during the crystallization.3. AlPO-PIL5and AlPO-PIL6have been synthesized by using(HDBAPA)(Ac) as the template and solvent. Elemental analysis and TG-DSCanalysis showed that the PIL was not decomposed in crystallization process.DBAPA+was occluded in the structure of the aluminum phosphates to keep thecharge balance.4. AlPO-PIL7, AlPO-PIL8, AlPO-PIL9and AlPO-PIL10have beensynthesized by using (H2TMEDA)(AC)2and (HMIBPA)(Ac) as the templateand solvent. Crystal structure analysis showed that AlPO-PIL7hastwo-dimensional layer structure; TMEDA+compensated the negative charge ofthe anionic network. AlPO-PIL9has one-dimensional chain structure with4-membered rings.