Coordination Assembly And Properties Of Extended Structures Based On Mental-Substituted Keggin-type Heteropolytungstates

Polyoxometalates(POMs)are intriguing polynuclear metal-oxide clusters.These metal-oxide clusters have received great scientific interest because of their unique structural,compositional diversities and excellent physicochemical properties,which have potential applications in the fields of chemistry,materials,environment,and biology,etc.As the most classical kind of POMs,Keggin-type heteropolytungstates have been widely investigated.The excellent performance units can be obtained by introducing other metal ions into the vacancy of lacunary Keggin-type heteropolytungstates.On these bases,metal-substituted Keggin-type heteropolytungstates used as inorganic building blocks to design and synthesis of POM-based extended structures become the popular research subjects in the realms of coordination chemistry and crystal engineering.In this paper,13 new extended structures based on mental-substituted Keggin-type heteropolytungstates have been synthesized,including 8 novel Ln-substituted Keggin-type phosphotungstates-based rare earth metal-organic frameworks and 5 novel{SiW9V3}-based extended structures coordinated by mental-organic species,characterized by IR,UV-Vis,elemental analysis,XRPD and single-crystal X-ray diffraction analysis.The electrochemical,luminescent,photocatalytic,and organic catalytic properties of the related products have also been investigated in detail.The contents of this paper are divided into two chapters,as follows:1.A series of Ln-substituted Keggin-type phosphotungstates-based rare earth metal-organic frameworks 1-8 have been synthesized based on {Ca6[P4W6O34]2},2,6-pyridinedicarboxylic acid(L1),1,4-bis(pyridinil-4-carboxylato)-1,4-dimethylbenzene(L2)and Ln(N03)3(Ln= La,Ce,Pr,Nd,Sm,Eu).According to the organic ligand is divided into the following second sections:(1)Six {PW11Ln}-based 3D rare earth metal-organic frameworks 1-6 have been prepared by the reaction of {Ca6[P4W6O34]2},2,6-pyridinedicarboxylic acid and Ln(N03)3(Ln= La,Ce,Pr,Nd,Sm,Eu):H[La4(L1)4(H2O)8(PW11LaO40)]·5H2O(1)H[Ce4(L1)4(H2O)8(PW11CeO40)]·5H2O(2)H[Pr4(L1)4(H2O)8(PW11PrO40)]·5H2O(3)H[Nd4(L1)4(H2O)8(PW11NdO40)]·5H2O(4)H[Sm4(L1)4(H2O)8(PW11SmO40)]·5H2O(5)H[Eu4(L1)4(H2O)8(PW11EuO40)]·5H2O(6)Singel-crystal X-ray diffraction analysis reveals that compounds 1-6 dispiay 3D structure constructed by the coordination interaction between the Ln-substituted Keggin-type anion[PW11LnO40]5-as inorganic ligand and Ln-2,6-pydc species.The optical properties imply the energy bands(Eg)of compounds 1-6 are 3.38,2.64,3.47,3.45,3.54 and 3.58 eV,respectively.The fluorescent properties of compounds 4-6 show the emission peaks of the corresponding Ln ions at room temperature.Photocatalytic measurement shows that compounds 1,2,4-6 can accelerate the photodegradation of RhB.Compound 1 has the best photocatalytic effect on RhB solution with the degradation rate of 98%,while compound 3 exhibits adsorption activities for RhB solution with the adsorption rate of 62.6%.They exhibit good electrocatalytic oxidation behaviours toward dopamine,ascorbic acid and sodium nitrite,respectively.Additionally,compounds 1-6 exhibit good catalytic performances for the cyanosilylation of 2-methylbenzaldehyde,3-methylbenzaldehyde,4-methylbenzaldehyde,4-tert-butylbenzaldehyde and 4-anisaldehyde,the conversions rates all over 98%.(2)Two {PW11Ln}-based 3D rare earth metal-organic frameworks 7 and 8 have been prepared by using 1,4-bis(pyridinil-4-carboxylato)-1,4-dimethylbenzene instead of 2,6-pyridinedicarboxylic acid:H11[Pr(L2)2(H2O)4(PW11PrO40)2]·5H2O(7)H11[Nd(L2)2(H2O)4(PW11NdO40)2]·5H2O(8)Singel-crystal X-ray diffraction analysis reveals that two Ln-substituted Keggin-type anions[PW11LnO40]5-form a dimer which connected by terminal oxygen atoms,and the dimer further coordinated with ligand L2 and rare earth metal to form a {PW11Ln}-based 3D extended structure.The optical properties indicate the energy bands(Eg)of compounds 7 and 8 are 3.39 eV and 3.46 eV,respectively,implying that they have the properties of broad band semiconductor materials.Photocatalytic measurements show that compounds 7 and 8 can accelerate the photodegradation of RhB,the decolorization rate of RhB solution can achieve 88.5%and 57.9%,respectively.Compounds 7 and 8 exhibit good catalytic performances for the cyanosilylation of 2-methylbenzaldehyde,and the conversion can reach 98.94%and 98.05%.2.Five novel {SiW9V3}-based extended structures 9-13 have been prepared based on the vanadium-substituted polyoxoanions[SiW9V3O40]6-as precursors,different nitrogen-containing organic ligands 1,1'-(1,4-phenylene-bis(methylene))-bis(pyridine-4carboxylic acid)(L2),1,1'-bis(4-carboxylatobenzyl)-4,4-bipyridinium dichloride(L3),para-diazine(L4),2,2'-bipyridine(L5),pyrrolidin-2-ylimidazole(L6)and metal cations(Cu2+?Ag+?Pr3+):H8[Cu3(L2)3(H2O)6(OH)2][SiW9V3O40]·7H2O(9)H6[Pr(L3)2(SiW9V3O40)]·10H2O(10)[Ag6(L4)4(H2O)3(SiW9V3O40)]· 3H2O(11)[Cu4(L5)5(H2O)2(OH)2][Cu(C2O4)0.5](SiW9V3O40)·6H2O(12)H4[Cu(L6)4(SiW9V3O40)]·2H2O(13)In compound 9,tetranuclear copper subunits and ligand L2 form a two-dimensional structure,and[SiW9V3O40]6-act as templates to fill the hole in the plane.Compound 10 displays a 1D structure based on the coordination interaction of[SiW9V3O40]6-,Pr3+ and ligand L3.Compound 11 exhibits a 3D{SiW9V3}-based extended structure,each polyanion[SiV3W9O40]6-is connected with 10 silver ions,and futher coordinated with ligand L4 to form a three-dimensional structure.Compound 12 exists two building units tetranuclear copper Cu4(OH)2(H2O)2 and binuclear copper Cu2(C2O4),the two building units are coordinated with[SiV3W9O40]6-to form a dimer.In compound 13,each copper atom connects with four ligands L6 to form a windmill shape,and then it connects with adjacent polyanion[SiW9V3O40]6-to form a one-dimensional chain structure.The band gap values(Eg)of compounds 9-13 are 2.14 eV,2.21 eV,2.15 eV,2.21 eV and 2.28 eV,respectively,implying that they have the properties of narrow band semiconductor materials.Photocatalytic measurements show that compounds 9-13 can accelerate the photodegradation of RhB solution.Compounds 10 and 12 have good photocatalytic properties for MB solution.In particular,the decolorization rate of MB solution can achieve 85.05%and 80.45%.Compounds 11 and 12 exhibit good electrocatalytic activities toward the reduction of hydrogen peroxide and sodium nitrite.Otherwise,the catalytic behaviours on the oxidation of alkenes of compounds 9-13 have also been investgated.Results show that compound 13 has the best catalytic effect in the catalytic reaction of cyclooctene,and the conversion rate is 73.06%.Compound 10 has the best catalytic activity on the oxidation of styrene,and the conversion rate is 43.03%.