Design,Synthesis And Properties Of Rare Earth Metal-organic Frameworks Based On Vanadium Substituted Dawson-type Phosphotungstates

Metal-organic frameworks(MOFs)have been attracted the attention of researchers and become one of the polular research subjects in the realms of chemistry and materials in recent years because of their important application in the fields of optics,electricity,magnetism,biology,medicine and catalysis.Polyoxometalates(POMs)are regarded as one kind of outstanding inorganic building block for the design and synthesis of new POM-based MOFs with a variety of structural motifs and potential applications due to their attractive discrete,nanoscale-sized,and an unmatched range of physical and chemical properties.So the design and synthsis of POM-based MOFs is one of the important parts of coordination chemistry and crystal engineering.Among them,the synthesis of POM-based rare earth metal-organic frameworks is challenging topics by the introduction of rare earth metals with excellent photoelectric properties.In this paper,21 new POM-based rare earth metal-organic frameworks 1-21 were synthesized by hydrothermal method and characterized by IR,UV spectroscopy,elemental analysis,XRPD and single-crystal X-ray diffraction analysis,where POM building block is vanadium-substituted Dawson-type heteropolytungstate and the organic ligand is pyridinedicarboxylate.The magnetic,electrochemical,luminescent and organic catalytic properties of the related products were investigated.The contents of this paper are divided into two chapters,as follows:1.Fifteen new POM-based rare earth metal-organic frameworks 1-15 were synthesized by hydrothermal method with[P2W17VO62]7-as building blocks.According to the organic ligand is divided into the following three sections:(1)Eight POM-based rare earth metal-organic frameworks 1-8 were synthesized based on 2,6-pyridinedicarboxylic acid liangd,K7[?2-P2W17VO62]·18H2O and Ln(N03)3(Ln=Pr,Tb,Gd,Eu,Ce,Sm,Dy,Nd).[Pr4.5(2,6-pydc)3(H2O)20.5(OH)0.5(P2W17VO62)](1)[Tb4.5(2,6-pydc)3(H2O)20.5(OH)e.5(P2W17VO62)](2)[Gd4.5(2,6-pydc)3(H2O)20.5(OH)0.5(P2W17VO62)](3)[Eu4.5(2,6-pydc)3(H2O)20.5(OH)0.5(P2W17VO62)](4)[Ce4.5(2,6-pydc)3(H20)20.5(OH)0.5(P2W17VO62)](5)[Sm4.5(2,6-pydc)3(H20)20.5(OH)0.5(P2W17VO62)](6)[Dy4.5(2,6-pydc)3(H20)20.5(OH)0.5(P2W17VO62)](7)[Nd4.5(2,6-pydc)3(H20)20.5(OH)0.5(P2W17VO62)](8)Singel-crystal X-ray diffraction analysis reveals that the structures of 1-8 exhibit novel 3D POM-based rare earth metal-organic frameworks constructed by the coordination interaction between the Dawson polyoxoanions[P2W17VO62]7-as sexadentate ligands and Ln-2,6-pydc species.Both 1 and 2 exhibit dominant antiferromagnetic interactions,and good electrocatalytic activities for nitrite reduction.The luminescent properties of compounds 2,4,6 and 7 were investigated in both the solid state and aqueous solution at room temperature.(2)Four POM-based rare earth metal-organic frameworks 9-12 were synthesized based on 2,5-pyridinedicarboxylic acid liangd,K7[?2-P2W17VO62]·18H2O and Ln(NO3)3(Ln= Eu,Sm,Tb,Gd)H3[Eu4(2,5-pydc)4(H2O)16(P2W17VO62)]·9H2O(9)H3[Sm4(2,5-pydc)4(H2O)16(P2W17VO62)]·9H2O(10)H3[Tb4(2,5-pydc)4(H2O)16(P2W17VO62)]·9H2O(11)H3[Gd4(2,5-pydc)4(H2O)16(P2W17VO62)]·9H2O(12)Compounds 9-12 are basically isostructural and feature a 3D POM-based metal-organic framework containing 1D channels,which formed through the coordination interaction of Ln,2,5-pydc2-and[P2W17VO62]7-as tetradentate ligands.The fluorescent properties of compounds 9-11 were investigated in both the solid state and aqueous solution.Compounds 9 and 10 show red fluorescence and compound 11 is green fluorescence.(3)Three POM-based rare earth metal-organic frameworks 13-15 were synthesized based on 3,5-pyridinedicarboxylic acid liangd,K7[?2-P2W17VO62]·18H2O and Ln(NO3)3(Ln=Eu,Tb).H4[Eu3(3,5-pydc)3(H20)15(P2W17VO62)]·6H2O(13)H4[Tb3(3,5-pydc)3(H20)15(P2W17VO62)]·6H2O(14)H5[Tb4(3,5-Pydc)5(H20)12(P2W17VO62)]·11H2O(15)Compounds 13 and 14 are basical isostructure and exhibit a porous 3D framework with cooperative intermolecular supramolecular interactions between[P2W17VO62]7-and Ln-3,5-pydc specie.The structural feature of 15 is that it forms a 3D POM-based rare earth metal-organic framework containing[P2W17VO62]7-as tetradentate ligands.The luminescent properties of compounds 13-15 were investigated at room temperature.Compound 13 is red fluorescence and compounds 14 and 15 show green fluorescence under UV light.2.Six new POM-based rare earth metal-organic frameworks 16-21 were synthesized by hydrothermal method using 2,5-pyridinedicarboxylic acid liangd,KgH[P2W15V3O62]·9H2O and Ln(NO3)3(Ln= Pr,La,Nd,Ce,Eu,Sm)as the starting materials.H[Pr4(2,5-pydc)2(H20)18(P2W15V3O62)]·12H2O(16)H[La4(2,5-pydc)2(H20)18(P2W15V3062)]·12H2O(17)H[Nd4(2,5-Pydc)2(H20)18(P2W15V3062)]·12H2O(18)H[Ce4(2,5-pydc)2(H20)18(P2W15V3062)]·12H2O(19)H3[Eu5(AcX2,5-pydc)4(H2O)14(P2W15V3O62)]·7H2O(20)H5[Sm4(2,5-pydc)4(H20)16(P2W15V3O62)]·7H2O(21)Compounds 16-19 are basically isostructural and feature a 2D POM-based metal-organic framework,which formed through the coordination interaction of octametallic Ln-2,5-pydc units and[P2W15V3]9-as heptadentate ligands.Compounds 17-19 exhibited good catalytic performance for the cyanosilylation of aldehydes.Compounds 20 and 21 show all 3D POM-based metal-organic frameworks containing[P2W15V3]9-as heptadentate ligands for 20 and tetradentate ligands for 21.The luminescent properties of compounds 20 and 21 were investigated.