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Syntheses And Structures Of Novel Microporous Germanate Molecular Sieves

Posted on:2004-07-17Degree:DoctorType:Dissertation
Country:ChinaCandidate:Y M ZhouFull Text:PDF
GTID:1101360092475010Subject:Inorganic Chemistry
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Nowadays, the application of microporous materia1s is not only confined to thefields of catalysis, gas adsorption and separation, but also widely extended tonon-linear optical materials, semiconductor materials, microreactors etc. There isalways a genera1 interest in discovering new open-framework materials in nove1compositional domains.While extensive commeriacal success has been achieved through the use oforganic molecules in the synthesis of aluminosilicate zeolites, the synthesis of thegermanium-based zeolite structures by using organic structure-directing agents is aIargely unexplored area. Germanates are of particuIar interest because they havemetal-oxygen bond distances significantly greater than those in silicate-based material.The large T-O distances in germantes lead to smaller T-O-T angels. In this work, weconcentrated in developing germanium--based zeolite-like structures. Our works is notlimited to expansion of known zeolite structures into a new compositional domain butalso develop a synthesis strategy to prepare structures with previously unknownframework topologies.In this thesis, we reported more than dozen germanate zeolite structures preparedwith organic amines or inorganic cations as structure-directing agents. These newmaterials exhibit several interesting structural features such as helical chains andodd-membered rings. Three member ring in these materials is believed to be the keyto frameworks with large pore and the lowest possible framework density. In thesegermanates, framework are fOrmed by GeO5 trigonaI bipyramids or GeO6 octahedra,as we1l as GeO4 tetrahedra.In the solvothermal system, using DMF as solvent and TREN as template, a new24-membered-ring germanate (FDU-4) was synthesized. FDU-4 is the first germanatezeo1ite-like structure with the 24-member ring channels and it has a previouslyunknown framework. The framework density of FDU-4 is l l. l, which is one of thelowest framework densities. Two kinds of channels in FDU-4 arranged inRqX7M1:$&itx bq Rclose-packed hexagonal, honeycomb arrays, just as in the mesoporous materials. Itimply that the fOrmation of mesoporous materials with two unifOrm, ordered, porechanne1s and microporous crysta11ine wal1s is possib1e. Another 1arge poregermanate (FDG-2) which have three-dimension 12-member rings was synthesizedusing DMF as solvent and DABCO as template.Using 1,4-dioxane and water as solvent and TREN as template, a noveIgermanate (FDG-9) was synthesized. Its structure is constructed from Ge7 clusterunits 1inked into lD seven member ring channels along direction (l l0). Another novelgermanate (FDG-10) was prepared by heating a mixture of germanium dioxide,ethylene glycol, water and 1,6-hexamethylendiamine. FDG-10 is the firstgermanate-based structure with 1l-rings. Its structure is constructed from Ge6 clusterunits in which GeO3 trigona1 pyramid is first observed.Using TMAOH and ethylenediamine as template, three germinates (FDG-l1,FDG-l2, FDG-l3) with soda1ite topo1ogy were obtained. Because of the strongtemplate action of ethylenediamine, FDG-12 and FDG-13 have unusuaIIy lowframework symmetry for a sodalite structure. The cubic FDG-1l and the TriclinicFDG-l2 and FDG-l3 are ideal examples of the structural control of the inorganicframework by structure directing amines.Two layer germanate (FDG-16 and FDG-l7) were prepared using4-aminoetheyl-pyridine and Na+ as template. FDG-l6's structure is bui1t from twodimensional sheet with 3-ring and 9-ring, just like that in UCSB-9L. FDG-l6 wassynthesized in fluoride-free media. FDG-l7 is a new layer germanate built from sheetwith 6-ring.In the Ga(Al)-Ge-P-O system, using l,3-propane diamine (PDA) as template,three chain zeo1ite-type structures, FDG-l 8, FDG-l9 and FDG-20, were synthesizedrespectivily. FDG-20 is the first gallium germanium phosphate. In FDG-l9, chains arelinked by hydrogen bonds each other to fOrm two dimensional layer firs...
Keywords/Search Tags:Microporous material, Germanate, Hydrothermal synthesis, Solvothermal synthesis, Crystal structure
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