Preparation And Photocatalytic/Electrocatalytic Properties Of Polyoxometalate-based Materials Modified By D/f Metals-Organic Amine Ligands

In this thesis,six new polyoxometalate?POM?-based materials decorated by d or f metals,supplemented by N-azole ligands and carboxyl/N-azole ligands have been synthesized under hydrothermal technique.And they have been structurally characterized by single crystal X-ray diffraction,IR spectra,X-ray powder diffraction and elemental analyses,etc.The electrochemical properties,electrocatalytic hydrogen evolution reaction?HER?activities and photocatalytic properties of some compounds have been studied.We have discussed the influence of the configurations of metal ion coordination polyhedra,the connection of polyoxometalates and metals,the charge density of POMs,the steric hindrance of metal-ligand subunits,the configuration of the ligands and introduction of carboxylic acid auxiliary ligands/carboxylic acid functional groups on the structures of POM-based materials.The relationship between structures and properties is also carried out.The results are as follows:1.POM-based hybrid materials modified by d10 metal-N-azole organic subunits.By introducing different Keggin polyoxoanions [BW₁₂O₄₀]5-(BW₁₂),[Ge W₁₂O₄₀]4-(Ge W₁₂)into the Ag and ppz reaction system,compounds 1 and 2 have been synthesized on the basis of hydrothermal methods under the same reaction conditions.By tuning different metal and introducing and Keggin polyoxoanion [PW₁₂O₄₀]₃-(PW₁₂)into the Cu and ppz reaction system,compound 3 have been synthesized under the same reaction conditions.The molecular formulas of compounds 1-3 are as follows:[Ag₄?ppz?₄(BW₁₂O₄₀)][Ag?ppz?₂]?1?[Ag₃?ppz?₄][HGeW₁₂O₄₀]·H₂O?2?[CuI₂?ppz?₄][HPW₁₂O₄₀]·4H₂O?3?ppz=3-?pyrid-4-yl?pyrazoleCompound 1 is 1D chain structure that two neighboring Ag-ppz Z-type chains are connected by BW₁₂ clusters through covalent bonds.There are rhombic windows with a dimension of ca.13.3 × 14.9 ?2 in the BW₁₂-Ag-ppz chains.Moreover,a 3D supramolecular pore structure is achieved by massive intermolecular ????? stacking interactions.Compound 2 shows an interesting 2D microporous layer with cantilever chains.Compound 3 exhibits a 1D poly-pentant inorganic-organic chain and the adjacent chains are connected to each other to achieve a porous 2D layer via the ????? stacking interactions of the ppz ligands.Compounds 1 and 3 have been taken as examples to study their electrocatalytic properties.The electrocatalytic properties of compounds 1 and 3 are investigated.The results indicate that they may be potential bifunctional electrocatalysts,which can not only catalyze the oxidation of biologic molecules AA,but also can catalyze the reduction of inorganic molecules.Compounds 1 and 3 have better potential applications in detection of IO3-.2.POM-based hybrid materials modified by d/f metal-carboxyl/N-azole organic subunits.By introducing different kinds of polyoxoanions [W6O19]2-?W6O19?,[Si W₁₂O₄₀]4-(Si W₁₂)into the Cu+ox+bis?N-azole?reaction system,compounds 4 and 5 have been synthesized on the basis of hydrothermal methods under the same reaction conditions.By using f metal Ce and introducing bimba ligand containing both carboxyl and N-azole into the Ce3+ and [H₂W₁₂O₄₀]6-(W₁₂)hydrothermal reaction system,compound 6 has been obtained.The molecular formulas of compounds 4-6 are as follows:[Cu₂?bimb?₂?ox?]?W6O19?·10H₂O?4?[Cu₂?bbtz?₂?ox?][H₂Si W₁₂O₄₀]·12H₂O?5?[Ce₂?H₂L?₂?H₃L?₂?H₂O?10(H₂W₁₂O₄₀)₂]·4H₂O?6?bimb=1,3-bis?1-imidazoly?benzenebbtz=1,4-bis?1,2,4-triazol-1-ylmethyl?benzenebimba=HL=C₁₃H₁₀N₄O₂ = 2,5-bis?imidazol-1-yl?benzoic acidCompound 4 represents the first example of Linqvist intercalation compound.Compound 5 exhibits a 3D POMOF architecture with cavities,and the size of each cavity ca.10.6 × 4.8 ?2.Compound 6 shows dimeric structure.The electrocatalytic property of compound 4 is investigated.The result indicates that compound 4 has the stable and effective electrocatalytic activity towards the reduction of NO₂-in a wide concentration range.Based on the study of its electrochemical properties,the HER catalytic activity of compound 4-doped XC-72R?1:1?modified electrode?4-GCE?50 wt %??has also been evaluated by electrochemical experiments.The result shows that 4-GCE?50 wt %?has excellent eletrocatalytic capability to HER.Thus,compound 4 is a promising non-noble-metal catalyst to improve HER activity.Meanwhile,the photocatalytic properties for compound 5 are also carried out.It is obvious that compound 5 exhibits higher photocatalytic activities in the photodecomposition of Methylene Blue?MB?organic dye under visible irradiation and UV irradiation.Therefore,compound 5 is an active photocatalyst for the degradation of MB under visible irradiation.