Research On Synthesis And Properties Of 3d-4f Heterometal-organic Frameworks

Metal-organic frameworks(MOFs)belongs to the framework material,which is formed by connecting inorganic metals and organic ligands based on coordination bonds.The differences in size,structure and functional groups of organic ligands endows MOFs with ever-changing structural characteristics,and also makes MOFs show broad application prospects in adsorption and separation,drug delivery,magnetism,sensing,catalysis and other fields.Transition metals and rare earth metals coexist in 3d-4f MOFs,which show more complex structures and more interesting properties than single metal MOFs.In view of the great differences in coordination habits between transition and rare earth metals,5-(1H-tetrazol-5-yl)isophthalic acid(H₃TZI),a ligand containing both nitrogen and oxygen,was chosen to synthesize two series of Co-Ln and Zn-Ln,and there was a total of 14 novel3d-4f MOFs through coordination self-assembly.Meanwhile,their magnetic properties,adsorption properties and optical properties had been deeply studied.It is divided into the following two parts:1.Study on Magnetic Properties and Dye Adsorption and Separation Properties of Co-Ln MOFs with H₃TZI Ligand5 isomeric 3d-4f MOFs[(CH₃)₂NH₂]₄[Co₃Ln₃(OH)(TZI)₆(H₂O)₆]·2DMA·16H₂O(Co-Ln,Ln=Eu(1),Gd(2),Tb(3),Dy(4),Ho(5))were synthesized by self-assembling coordination Co^? and Ln ^?metal ions with H₃TZI ligand.There are 4 free[(CH₃)₂NH₂]⁺countercations in a non-repeating unit in the MOFs structure,which makes the framework as an electron-rich anion,and a large number of DMA and H₂O molecules are free in the framework structure,which guides us to study its adsorption of cationic dyes.It is found that the anionic MOFs can selectively adsorb the cationic dye methylene blue.In addition,the magnetic properties of this series of MOFs are studied,and it is found that they all transfer antiferromagnetic coupling,and CoDy(4)and CoHo(5)show slow relaxation behavior at low temperature.2.Study on Optical and adsorption properties of Zn-Ln MOFs with H₃TZI ligandA series of 3d-4f MOFs were synthesized using H₃TZI as ligand to coordinate Zn²⁺and Ln³⁺metal ions at the same time.Their molecular formula is[Zn₃Eu_xTb_2-x(TZI)₄(DMA)₅(H₂O)₃]·4DMA(x=0(6),0.3(7),0.6(8),0.9(9),1(10),1.2(11),1.5(12),1.8(13),2(14)).Among them,Zn₃Tb₂(6)and Zn₃Eu₂(14)can sense Fe³⁺and TNP by fluorescence quenching.At the same time,Zn₃Tb₂(6)was used as a representative to study the dye adsorption and iodine adsorption performance of MOFs.The results showed that the series of MOFs could effectively remove neutral red dyes in ethanol and iodine in cyclohexane solution.On the basis of synthesizing Zn₃Tb₂(6)and Zn₃Eu₂(14),doping different proportions of Eu³⁺and Tb³⁺ions to obtain MOFsZn₃Eu _xTb_2-x(7-13).Among them,the CIE color coordinates of Zn₃Eu_1.5Tb_0.5(12)at 298 nm are(0.33,0.33),which is just the coordinate of pure white light.On this basis,a white light emitting diode(WLED)is fabricated.