Syntheses, Characterization, And Detemplation Of Transition Metal Aluminophosphate Microporous Compounds

Aluminophosphate molecular sieves （AlPOs） have become an important familyof zeolitic materials since discovered by Wilson et al. in1982. Various metal atomsare introduced into the framework of AlPOs to partially replace the lattice Al and Patoms, forming heteroatom-containing aluminophosphate molecular sieves, whichproduce rich structural and compositional diversity, acid sites, redox centers and otherpromising properties such as optics and magnetism in the framework. These materialsare typically synthesized under hydrothermal/solvothermal conditions in thepresence of organic templates. The organic templates are occluded in the channels tostabilize the whole structure and balance the negative charge of the framework,interacting with the host framework through electrostatic, van der Waals andhydrogen-bondings. The inorganic framework with high substituted content tends tocollapse during the detemplation, which significantly limit the application of suchtransition metal substituted aluminophosphates. In this thesis, we aim to explore somenovel aluminophosphatethe microporous zeolites, and further investigate thedetemplation of these materials. We have successfully synthesized a series of noveltransitional-metal substituted aluminophosphates, and the detemplation aniron-containing aluminophosphate with LAU topology is carefully studied.The main results in this thesis are summarized as follows:1. Two heteroatom-containing open-framework aluminophosphates,（C₃H₄N₂）₂FeAl₃P₄O₁₆and （C₃H₄N₂）₂CrAl₃P₄O₁₆（denoted as MAPO-CJ50, M=Fe,Cr）, have been synthesized by using imidazole as template in the solvothermal system.The structure of FeAPO-CJ50is determined by single-crystal X-ray diffraction, andits analogue structure CrAPO-CJ50is identified by powder X-ray diffraction. The3-dimensional framework of MAPO-CJ50, constructed by MO₄N₂octahedra, AlO₄ tetrahedra, and PO₄tetrahedra, contains interconnecting10-and8-ring channels.Imidazole molecules are coordinated with framework M³⁺ions and interact with eachother through π-π stacking interactions in the channels. These two compounds showphotoluminescent properties due to ligand-to-metal charge transfer. Magneticmeasurements reveal that there are antiferromagnetic interactions between M³⁺ions inthe frameworks of FeAPO-CJ50and CrAPO-CJ50.2. Iron （II）-substituted LAU-zeotype aluminophosphate molecular sieve （denotedas FeAPO-LAU） was synthesized successfully by using imidazole as template in thesolvothermal system. The detemplation process was studied to elucidate the stabilityand microporous characteristics of FeAPO-LAU. In situ temperature-dependent X-raydiffraction analyses indicated that the framework of FeAPO-LAU possessed higherthermal stability and maintained the framework integrity until923K. The organictemplates could be removed by stage-temperature-programmed calcination usinglower heating rate in O2atmosphere,which gave rise to the sample with surface areasof ca.105m²/g. NH3-temperature programmed desorption （NH₃-TPD） analysisshowed that detemplated FeAPO-LAU had a weak acidity. Magnetic measurementrevealed that as-synthesized and detemplated FeAPO-LAU showed antiferromagneticbehaviour between Fe2+or Fe3+ions.3. A new open-framework iron-containing aluminophosphate (C₄H₁₂N₂)₂[Fe₂Al₅P₈O₃₂]·H₂O （denoted as FeAPO-CJ51）, with mixed-valent iron（II, III） hasbeen synthesized by using piperazine as the template. The structure is determined bysingle-crystal X-ray diffraction, and further characterized by X-ray powder diffraction,elemental （ICP, CHN）, thermogravimetric （TG）, and M ssbauer spectroscopyanalyses. The3-dimensional framework of FeAPO-CJ51, constructed bymetal-centered （Fe/Al） MO_n（n=4,5,6） polyhedra, and PO₄tetrahedra, containsinterconnecting8-ring channels along [010] and [001] directions, respectively.Protonated piperazine cations locate in the8-ring channels to compensate the negativecharge of the anionic framework. M ssbauer and magnetic susceptibilitymeasurements show that equal amounts of Fe²⁺ and Fe³⁺ ions are present, whichundergo a long-range antiferromagnetic interactions. 4. An open-framework ironophosphates C₁₂H₄₀N₆Fe₈O₄₂P₁₄（OH）₁₄（H₂O）₆（denoted as FePO-CJ52） has been synthesized by using1,4-butyl diamine as thetemplate. The structure is determined by single-crystal X-ray diffraction, and furthercharacterized by X-ray powder diffraction, elemental （ICP, CHN）, thermogravimetric（TG）, and M ssbauer spectroscopy analyses. The3-dimensional framework ofFePO-CJ52, constructed by FeO₆, FeO₅（H₂O） octahedra and PO₄tetrahedra, contains12-ring channels along [100] directions. M ssbauer and magnetic susceptibilitymeasurements show that Fe3+ions are present, which undergo a long-rangeantiferromagnetic interactions.