Ionothermal Syntheses And Characterizations Of Inorganic Open-Framework Compounds

Inorganic open-framework materials such as molecular sieves have been extensively used in many industrial processes such as catalysis, adsorption and separation. Therefore, the preparation of new inorganic open-framework materials is one of the most important fields for the material science. Recently, new types of open-framework materials such as metal phosphites and metal borophosphates with rich structural varieties have been extensively studied. Besides the traditional applications in catalysis, adsorption and separation based on the homogeneous porosity in the structures, these new materials have shown great potential applications in optics, electronics and magnetism. More and more novel open-framework materials have been prepared through the hydro/solvothermal methods.The emergence of new synthetic methods always means the synthesis of many new materials. Ionic liquids are electrovalent bonded compounds with completely different chemistry from the traditional solvent such as water/alcohols. Ionic liquids show some advantages such as low vapor pressure, high thermal stability and good dissolution ability compared to the water/alccohols. Very recently, the new ionothermal method using the ionic liquids as the solvent and/or the template has been developed for the synthesis of inorganic open-framework materials. The successful ionothermal synthesis of several microporous aluminophosphates has shown great potential of the ionothermal method for the preparation of new inorganic open-framework materials. However, the application of ionothermal method for preparation of new open-framework materials is still of challenge. Great efforts are needed for the further research.My thesis is mainly focused on the preparation of novel microporous aluminophosphates, metal phosphites and borophosphates with new structures, new composition and new properties by using the ionothermal method. Main achievements are as follows:1. A new aluminophosphate [Emim][MiaH][Al6P7O27(OH)] (denoted as JIS-1, Jilin Ionothermal Synthesis-1) has been prepared using the co-templating ionothermal method. We use the organic amine (N-methylimidazolium) as a cooperative structure directing agent in the ionothermal system with ionic liquid (1-ethyl-3-methylimidazolium bromide, [Emim]Br) as solvent. The alternating connection of Al-centered polyhedra and P-centered tetrahedra constructs the open-framework structure of JIS-1. It is featured by two kinds of 4,6,8-net layers. The structure possesses three dimensional channel system with 10-, 10- and 8-ring channels along the a, b and c directions, respectively. Both the additive amine and cations of ionic liquid have been occurred in the channels as templates. JIS-1 is the first aluminophosphate with a novel Al/P ratio of 6/7. Further, we enumerate all the possible combination for the Al and P coordination for the aluminophosphates with the same Al/P ratio of 6/7.2. We have presented the ionothermal synthesis of an open-framework nickel phosphite 5H3O·[Ni8(HPO3)9Cl3]·1.5H2O (JIS-3) by using ionic liquid as the solvent. The new compound has extra-large 18-ring channels in the framework. Its structure features 2D nickel-oxygen/chloride 18-ring layers composed of alternating face-sharing dimers of Ni(1)-centered octahedra and edge-sharing Ni(2)-centered octahedra. These layers are further pillared by pseudo-pyramidal HPO3 groups to form the 3D open framework. Magnetic measurements show that JIS-3 orders antiferromagnetically with spin-flop transition at a befitting applied field. Measurements on aligned single crystals indicate that the spins in the 2D nickel-oxygen/chloride 18-ring layers are oppositely oriented, and the magnetic moments are oriented to the easy c axis.3. We have presented the spontaneous ionothermal crystallization of a novel chiral open-framework borophosphate (NH4)2[HBP2O8] (JIS-2). JIS-2 contains intersecting 12-ring channels formed by helical chains. The chiral structure can be reduced into an achiral diamond net. The interactions between extra-framework ammonium cations and the framework play a key role in the chiralization of JIS-2. Ion-exchange experiments show that the framework was kept intact with extra-framework ammonium cations partially exchanged by K and Cs ions. 4. Three novel open-framework metal borophosphates: [Na6Co3B2P5O21Cl] H2O (JIS-4), K5Mn2B2P5O19(OH)2 (JIS-5), (NH4)8[Co2B4P8O30(OH)4] (JIS-6) have been prepared by using the same ionic liquid as the solvent. All these structures are based on similar cluster building units, transition metal-centered borophosphate heptamer. The structure of JIS-4 possesses 12-ring channels along the [100] direction and 8-ring channels along the [010] direction. It is interesting to note that JIS-4 contains both chlorine substituted CoO5Cl octahedra and CoO5 square pyramids which are rarely observed in the family of borophosphates. It is worth to note that both JIS-4 and JIS-5 have the same anionic partial structure of open-branched dreier-single ring heptamer with B/P ratio of 2/5, and JIS-4 is the first 3-D open-framework borophosphates in the family of borophosphates with B/P ratio of 2/5. The 2-D layer structure of JIS-6 containing 8-ring channels possesses 1-D anionic partial chain with B/P ratio of 1/2. It is noted that JIS-6 has unique anionic partial structure in contrast to the reported ones in the family of borophosphates. Experiments show that the amount of water contained in the ionothermal system plays an important role for the rate of crystallization and the final product.5. Three new aluminophosphate compounds: [ImH]3[Al3P4O16] (JIS-7), H3O[ImH][MimH][Al3P4O16]·(JIS-8) and H3O[Dmim]2[Al3P4O16] (JIS-9) have been prepared ionothermally using different amines as the structure-directing agents. All the three two dimensional compounds contain the same 4,6,8-net in the structures. Both the ionic liquid cations and additive amine co-exist between the adjacent layers in JIS-8. However, only one kind of template, protonated imidazole (amine) and 1,2-dimethylimidazolium (ionic liquid cations), exists in the structure of JIS-7 and JIS-9, respectively. It is interesting that both the amines and the ionic liquid cations haveπ–πsupramolecular interaction between the adjacent template molecules.