Synthesis And Characterization Of Crystalline Al₁₃ Based Salts With Varied Components And Multimorphologies

[AlO4Al12(OH)24(H2O)12]7+ (Al13) polyoxocations with Keggin structure play an important role in modern material chemistry. Polyoxometalates, one of the typical inorganic metal-oxide clusters, play a strategic role in the material science due to their novel compositions, structures and applications, e.g. novel catalysts, photo-electro-magnetic materials, medicine and so on.Four crystalline Al13 based salts were synthesized via a direct mixing route, the interactions of the crystalline Al13 based salts include the ionic electronic interactions, van der Waals interactions and hydrogen bonds between the Al13 polyoxocations and relevant negative ions.1. Crystalline Al13 based sulfates: Uniform tetrahedral and fiber-like crystalline based sulfates were synthesized via a direct mixing and aging route. A given amount solution was direct mixed with Al13 solution pretreated at 60-80 ℃ and then aged at room temperature for 12 h. SEM images show that the size of tetrahedral crystalline Al13 sulfates prepared via a direct mixing way is 150-200 μm, which is almost 10 times larger than that via a traditional titration way (15-25 μm). The size of the fiber-like crystalline Al13 sulfates is 0.5-1 μm in diameter and up to 1000 μm in length. Based on the crystal growth unit model of anionic coordination polyhedron, a possible crystal growth mechanism for the tetrahedral crystalline Aln sulfates was discussed.2. Crystalline Al13 based molybdates: The crystalline Al13 based molybdates with multimorphologies were synthesized via a direct mixing and aging method. The heteropoly compounds of H3PMo12O40·nH2O, H4PMo11VO40·H2O and (NH4)6P2Mo18O62·nH2O were employed as the molybdate sources. The morphology and size of the molybdate crystals is trimetrical-prismy like (80×30 μm), star-like (30×10 μm) and leaf-like (500×150 μm). XRD patterns show that the crystalline Aln based molybdates are of high crystallinity, and have strong and sharp peaks (29) at 6.65°, 8.00° and 14.16°. However, when Na2MoO4-2H2O was employed, there are only amorphous clusters in a similar process. The chemical formula of the crsyatlline Al13 based molybdates is Na[AlO4Al12(OH)24(H2O)12][MoO4]4·8H2O. The probable crystal growth mechanism was proposed.3. Crystalline Al13 based V1 polyoxometalates (V1, H4PMo11VO40·H2O): Starlike and layer structures of Al13 based V1 polyoxometalates were synthesized by directly combining PMo11VO404- polyoxoanions and Al13 polyoxocations in aqueous solution without addition of any surfactant or template, followed stirring and aging treatments, respectively. SEM results show that the uniform starlike structures with sphere morphology are made of many column-like microcrystals with size about 1 ×9 μm through self-assembly, and the average size of the superstructures is ca. 18-20 μm. The layer superstructures with whole size up to 200 μm are composed of many nanosheet structures with size about 250-500 nm, the clearance of the sheets is about 500-1000 nm, and the sheet structures are not completely paratactic, but some bended. XRD patterns indicate they are well crystallized crystals, and there are strong diffraction peaks at the 2θ range of 5-10°. The results of FTIR reveal that the Al13 based polyoxometalates hold the Keggin structures both of the Al13 and [PMo11VO40]4- ions.4. Crystalline Al13 based V3 polyoxometalates (V3, H4PMo9V3O40·nH2O): Based on the synthesis of the Al13 based V1 polyoxometalates, crystalline Al13 based V3 polyoxometalates were synthesized via a similar synthesis process, when H6PMo9V3O40·nH2O instead of H4PMo11VO40·nH2O. In the directly mixing and aging process, Al13 based V3 polyoxometalates with long needle-like porous structures were obtained. The size of the needle-like Al13 based V3 polyoxometalates is about 50 μm in diameter and 1-5 mm in length, respectively. The porous structures with about 1 μm diameter are irregularly distributed in the Al13 based V3 polyoxometalates. In the directly mixing and strongly stirring process, Al13 based V3 polyoxometalates with long and thin hexagonal lamellar structures were obtained. The length, width and thickness of the hexagonal lamellar structures are 100 μm, 10 μm and 0.5-2 μm, respectively.