The Synthesis And Adsorption Property Of MOFs Hybrids Based On Keggin-Type-Heteropolytungstates

Polyoxometalates(donated as POMs)possess oxygen-rich surface,nanoscale size,various chemical composition and well stability,which bestow excellent physical and chemical properties in various fields on itself.Therefore,the kind of inorganic building block was introduced into the metal-organic frameworks(donated as MOFs)to design and synthesize the polyoxometalates-based on metal-organic frameworks(donated as POMOFs),in order to obtain the composite material with the excellent physical and chemical properties of POMs and highly ordered topological structure.Meanwhile,the combination of POMs and MOFs may realize the synergistic effect of POMs and porous frame materials.Synchronously,it is hoped that new performance can be extracted from the synthetic complex topologies.In this article,eight novel compounds were synthesized by introducing heteropolytungstate into metal-organic framework system,and the synthesized compounds were characterized through the X-ray single crystal diffraction,Thermal gravimetric analysis,UV-Vis spectra and X-ray photoelectron spectroscopy.In addition,the research on the adsorption capability of eight synthetic complexes to diverse organic dyes were also performed.1.Three novel 3D supramolecular frame structures were synthesized by hydrothermal synthesis under the condition of strong acid:[Ce(H₂O)₃(BPDO)₃][Si W₁₂O₄₀](1)[Pr(H₂O)₃(HBPDO)(BPDO)₂][Si W₁₂O₄₀](2)[La(H₂O)₃(BPDO)₃][Si W₁₂O₄₀](3)Classic Keggin-type heteropolytungstate{Si W₁₂},as bidentate ligands in three compounds,coordinate with the adjacent rare earth cation to form 1D Re-POM inorganic chain which is similar to"Z"POMs in structure can be divided into two types in the light of diverse actions.One kind of POMs resides in the"grid"area through the W-Ot-Ce-Ot-W covalent bond,acting as a template in the construction of frame structures.Another kind of POMs located in the open area.On account of the connection of BPDO,large amounts of adjacent one-dimensional"Z"chains are linked to form a two-dimensional network structure.Finally,the two-dimensional network structure is combined with each other through intermolecular forces to form a three-dimensional layered structure.Adsorption studies showed that the three compounds exhibited good adsorption properties for MB⁺cationic dyes.2.Based on the synthesis of compounds in the previous chapter,{PW₁₂}of Keggin-type heteropolytungstates with similar size and structure characteristics was selected and introduced into the metal-organic frameworks which were constructed by transition metal ions and BPDO.Two three-dimensional POM-pillared composite materials with similar structure were obtained:[Cu₃(BPDO)₇(H₂O)][PW₁₂O₄₀]·2H₂O(4)[Co₃(BPDO)₇][PW₁₂O₄₀]·2H₂O(5)In the meantime,the adsorption properties of the above two complexes for MB⁺and MO^-were performed.It was indicated that two compounds showed certain adsorption effect for the cationic dye MB⁺,but almost no adsorption effect for the MO^-dye.3.Based on the synthesis of compounds above two chapters,heteropolytungstates with transition metal Co as the central heteroatom was selected and introduced into the lanthanide metal organic framework to obtain three 3D supramolecular materials with{Co W₁₂}as template agent:[Nd(BPDO)_4.5(H₂O)₂][Co W₁₂O₄₀]·3H₂O(6)[Ce(HBPDO)(BPDO)_3.5(H₂O)₂][Co W₁₂O₄₀]·2H₂O(7)[La(HBPDO)₂(BPDO)_2.5(H₂O)₂][Co W₁₂O₄₀]·2H₂O(8)A series of dye adsorption experiments were carried out on the three compounds to explore their adsorption properties for different dyes.