The Synthesis Of The Metal-organic Framework Materials Based On The Polyoxometalates And Their Functionality

The core work of this thesis is mainly focused on the synthesis and the exploitation onthe potential applications of the inorganic–organic composite materials which have alreadyattracted more and more research enthusiasm in recent years. Three POMs@MOF–typecomposites based on metal–organic frames (MOFs) and polyoxometalates (POMs) wereobtained by the way of hydrothermal synthesis. A further study of this kind of composites wascarried out for the adsorption and the selective adsorption of different organic dyes. Inaddition, two cases of heteropentametallic supramolecular framework materials were obtainedby an easy conventional method, providing a broader platform for the preparation of newcomposites. The main researchs are as follows:1. The synthesis of POMs@MOF–type functional materialsVarious polyoxometalates (POMs) were successfully immobilized to the mesoporouscoordination polymer MIL–101resulting in a series of POM–MOF composite materials,POMs@MIL–101(POMs=K4PW11VO40, H3PW12O40, K4SiW12O40). These materials weresynthesized by a simple one–pot reaction of Keggin–POMs, TMAH (tetramethylammoniumhydroxide), H2bdc (terephthalic acid), and Cr3+ions. XRD, FT–IR, TG, ICP and EDX havecollectively confirmed the successful encapsulation of POMs in the porous framework.Further, these composites POMs@MIL–101with different loading of POMs were achievedby variation of the POMs dosage.2. The study of the adsorption or selective adsorption of POMs@MOFNotably, the uptake capacity of MIL–101towards organic pollutants in aqueous solutionwas significantly improved by immobilization of hydrophilic POMs into cages of MIL–101.An uptake capacity of371mg/g, amount to that of the graphene oxide sponges, and muchhigher than that of the commercial activated carbon, was achieved at room temperature in5min when dipping20mg PW11V@MIL–101in the MB solution (100mL of100mg/L MBsolution). Further study revealed that the POMs@MIL–101composite materials not onlyexhibited a fast adsorption rate towards dye molecules, but also possessed of selectiveadsorption ability of the cationic dyes in wastewater. For example, the adsorption efficiencyof PW11V@MIL–101(10mg) towards MB (100mL of10mg/L) could reach98%in theinitial5min, and it could capture MB dye molecules from the mixture of the MB and MOwith similar size. Also, the POMs@MIL–101materials could be readily recycled and reused,and no POM leached in the dye adsorption process.3. The synthesis of heteropentametallic supramolecular framework materials Two organic–inorganic hybrid compounds with the formula{[MnIII(Salen)(H2O)]4MoO4}·Cl2·16H2O (1) and{[MnIII(Salen)(H2O)]4WO4}·(CH3COO)2·11H2O (2)(Salen=Di–[2–hydroxyl–3–methoxyl–benzaldehyde] ethylenediamine) have been synthesized andcharacterized by IR, UV–vis spectroscopy, TG analysis and single crystal X–ray diffraction.Structural analysis revealed that compounds1and2consisted of a [MoO4]2–or [WO4]2–building unit and four {[MnIII(Salen)(H2O)]+metal–organic moieties, resulting in thepenta–nuclear heterometallic tetrahedra cluster compounds. Further, the molecules of1or2are connected by the H–bonding interactions into a3D supramolecular porous frameworkpossessing two kinds of pores with the dimensions of8.96×6.262and15.2×7.032,respectively. Magnetic study revealed that they were antiferromagnetic.