Construction Of Luminescent Eu³⁺/Tb³⁺ Coordination Polymer And Its Fluorescence Sensing And Photocatalytic Degradation Properties

Lanthanide coordination polymers（Ln-CPs）,especially Eu³⁺/Tb³⁺as metal nodes,not only have the advantages of high porosity,large specific surface area,open active site,adjustable pore size,and good thermal and chemical stability.Ln-CPs have the advantages of lanthanide ion sharp and characteristic emission,large Stokes shift,long fluorescence lifetime and high quantum yield.Ln-CPs have a unique luminescence process(energy transfer from organic ligand to Ln³⁺),and the interaction between analyte and Ln³⁺or analyte and ligand will affect the luminescence intensity of Ln-CPs.Due to the diversity of organic ligands,Ln-CPs showed a variety of responses to different analytes.Based on this,Ln-CPs can be used as fluorescent sensing materials for metal cations,anions,antibiotics,nitro explosives and pesticides.At the same time,Ln-CPs can be used as photocatalyst for photocatalytic degradation of tetracycline pollutants to achieve the purpose of pollutant removal.In this thesis,Eu³⁺and Tb³⁺are used as metal nodes.5-（pyridin-2-ylmethoxy）isophthalic acid（2-H₂pyia）and 5-（pyridin-3-ylmethoxy）isophthalic acid（3-H₂pyia）were carboxylic acid ligands,1,10-phenanthroline（phen）,4,4’-Bipyridyl（4,4’-bipy）,imidazo[4,5-f][1,10]phenanthroline（IDP）,4,4’-bis（imidazol-1-ylmethyl）biphenyl（4,4’-bimp）,2,2’-Bipyridyl（2,2’-bipy）were nitrogen-containing ligands.Eight kinds of Ln-CPs materials were successfully synthesized by hydrothermal method.[Tb₂（2-pyia）₃（phen）₂（H₂O）]·H₂O（1）,[Tb（2-pyia）（Ac）（IDP）]（2）,[Tb₄（2-pyia）₆（HAc）_0.5（2,2’-bipy）（H₂O）_4.5]·（2,2’-bipy）·H₂O（3）,[Tb（2-pyia）（Ac）（H₂O）]（4）[Eu₂（3-pyia）₃（H₂O）₄]·（4,4’-bipy）·3H₂O（5）,[Eu₂（3-pyia）₂（Ac）₂（H₂O）₄]·（2,2’-bipy）_0.5·4.25H₂O（6）,[Eu（3-pyia）（Ac）（4,4’-bimp）]（7）and[Eu（3-pyia）（Ac）（H₂O）₂]·H₂O（8）.Their structures were analyzed and characterized by elemental analysis,single crystal X-ray diffraction,infrared spectroscopy（IR）,thermogravimetric analysis（TG）and XRD.Meanwhile,the fluorescence sensing and photocatalytic degradation properties of Ln-CPs were studied.1.Using Tb³⁺as metal node,2-H₂pyia as carboxylic acid ligand,phen,2,2’-bipy,IDP as nitrogen-containing ligand,four kinds of Tb-CPs（1-4）were successfully synthesized under hydrothermal conditions.The structure analysis of CPs 1-4 shows that CPs 1,3 and 4 are two-dimensional network structure,and CP 2 is one-dimensional chain structure.Fluorescence sensing experiments showed that CPs 1-3 responded to fluorescence quenching of Fe³⁺,CPs 1 and 3 responded to fluorescence quenching of Cr₂O₇^2-,tetracycline,2,4,6-trinitrophenol,CPs 2 and 4 responded to fluorescence quenching of cefixime,CP 2 responded to fluorescence quenching of p-nitrophenol,CP 4responded to fluorescence quenching of nitrobenzene.Both CPs 1-4 responded to fluorescence quenching of fluridine.The mechanism of the fluorescence response of CPs1-4 to the analyte was discussed as competitive absorption,photoinduced electron transfer and dynamic/static quenching.2.Using Eu³⁺as metal node,3-H₂pyia as carboxylic acid ligand,4,4’-bipy,2,2’-bipy and 4,4’-bimp as nitrogen-containing ligand,four kinds of Eu-CPs（5-8）were successfully synthesized under hydrothermal conditions.The structure analysis of CPs5-8 showed that CPs 5 and 7 were two-dimensional network structure,and CPs 6 and 8were one-dimensional chain structure.The fluorescence sensing experiments showed that CP 5 enhanced the fluorescence response of Cu²⁺,B₄O₇^2-,tetracycline and imidamine,and quenched the fluorescence response of pyrimethanil.CP 6 responded to enhanced fluorescence of Cu²⁺and imidamine,while nitrobenzene and pyrimethanil responded to fluorescence quenching.CP 7 responded to enhanced fluorescence of imidamine,and quenched fluorescence of ornidazole,nitrobenzene and fluridine.Response of CP 8 to fluorescence quenching of metronidazole,nitrobenzene and fluridine.The response mechanism of CPs 5-8 to the analyte was discussed.The fluorescence quenching mechanism may be a combination of competitive absorption,photoinduced electron transfer and dynamic/static quenching.The mechanism of fluorescence enhancement may be the combination of photoelectron transfer and weak interaction between analyte and ligand.3.The photocatalytic degradation performance on tetracycline of activated products of CPs 3 and 5 were studied.The photocatalytic degradation efficiency of CP 3 and its activated product were 84.29%and 96.07%,and the degradation efficiency of CP 5 and its activated product were 77.74%and 79.15%,respectively.The photocatalytic mechanism of the complexes and its activated products was also discussed.The results indicated that.O₂^-and h⁺were the main active species.