| Metal-organic frameworks(MOFs)are a class of coordination polymers with porous open framework,which usually produce fascinating topologies by metal nodes connecting with multiple functional organic linkers.Ratiometric lanthanide MOFs(Ln-MOFs)containing multiple luminescent centers exhibit excellent composite luminescent properties.Its fluorescent properties can be affected by some analyte,thus to achieve quantitative and qualitative fluorescence recognition and detection of the analyte.This thesis selected 1,3-bis(3',5'-dicarboxypheny l)benzene(H4ddb)as the ligand to synthesize three new isostructural luminescent Ln-MOFs in hydro(solvo)thermal reactions.The space group of Ln-Hddb is the three crystal system P-1,without diagonal unit[Ln(Hddb)(H2O)]·H2O is composed of a Ln3+ center,Hddb3+ ligand,a coordination water molecule and a lattice water molecule composition.These Ln-MOFs can rapidly detect Fe3+and 2,6-dipicolinic acid(DPA)with high sensitivity and selectivity,and durability.The thesis comprises of two main parts as follows:Part one.A hydrothermal reaction of H4ddb with Tb3+gave out a terbium-based MOF(Tb-Hddb).Tb-Hddb emitted green fluorescence at 490 nm(middle),545 nm(strong),583 nm(weak),and 621 nm,assigned to the characteristic transitions 5D4?7FJ(J=6-3)of Tb3+.Screening detected twenty-two optional ions,including seventeen metal cations(Na+,Ag+,Ni2+,K+,Ba2+,Pb2+,Co2+,Cd2+,Ca2+,Al3+,Zn2+,Mg2+,Mn2+,Cu2+,Cr3+,Fe2+and Fe3+)and five anions(Br-,I-,Ac-,Cl-,NO3),indicated that only Fe2+ can completely quench the fluorescence of Tb-Hddb.The sensitivity test of Tb-Hddb showed a linear response of I0/I=55.2061·CFe3++1.24077 in the CFe3+range of 3.3×10-4-0.033 mmol·L-1,and the limit of detection(LOD)is calculated to be 0.936 ?M.With sixteen metal of Na+,Ag+,Ni2+,K+,Ba2+,Pb2+,Co2+,Cd2+,Ca2+,Al3+,Zn2+,Mg2+,Mn2+,Cu2+,Cr2+,and Fe2+ and five non-metal ions of Br-,I-,Ac-,Cl-,NO3-as an interfered ions in the selective experiment,they did not influence the fluorescence quenching of Tb-Hddb by Fe3+,suggesting that detection performances of Tb-Hddb to Fe3+cannot be interfered by the selected interfered ions.A four-time quenching-recovery cycle in the durability test was carried out to check the durability of Tb-Hddb.The results shows that the emission intensities at 545 nm assigned to 5D4?7F5 of Tb3+can basically be recovered in the quenching-recovery cycle.Totally,Tb-Hddb can be regarded as a quantitative rapid Fe3+turn-off fluorescence sensor with high durability,selectivity and sensitivity.Part two.Hydrothermal reactions of H4ddb with Eu3+and Tb3+produced a series of hetero MOFs(Tb,Eu1-x,-Hddb).The powder X-ray diffraction(PXRD)spectra of TbxEu1-x-Hddb and single central Eu-Hddb are identical,indicating that the TbxEu1-x-Hddb has the same single crystal structure as Eu-Hddb and high phase purity.The factors of Tb3+:Eu3+ratio,pH value,and the MOF dosage on the DPA detection performances were investigated and Tbx-Eu1-x-Hddb were optimized as Tb0.875Eu0.125-Hddb.The optimized Tb0.875Eu0.125-Hddb showed high stability in organic solvents,HEPES buffer solution,NaOH and HCl solutions with pH=2-11.The fluorescence spectra of TbxEu1-x-Hddb showed the characteristic fluorescence of Eu3+(5D0?7FJ(J=1-4))and Tb3+(5D4?7FJ(J=6-3)).A linear response of I545/I613=0.0362·CDPA+0.3176 was revealed in the sensitivity test of Tb0.875Eu0.125-Hddb in the CDPA range of 100-1000 ?M with LOD calculated as 0.8494 ?M.It is clear that LOD(0.8494 ?M)of Tb0.875Eu0.125-Hddb with a wide linear range(0-100 ?M)is lower than or comparable to most reported MOF-based sensors.Seven interferents including BA,INA,MET,LYS·HCl,ASP,GLY,and ARG,did not influence its detection performances.The paper-based MOF sensor of Tb0.875Eu0.125-Hddb displayed obvious emission color conversions at CDPA=60 ?M,and a linear equation of G/R=0.01091·CDPA+0.12092 with LOD of 19.1 ?M through recognizing the RGB values of the paper-based MOF,showing a prospect in a rough on-site DPA detection.Therefore,Tb0.875Eu0.125-Hddb and its paper-based sensor are a ratiometric quantitative rapid DPA fluorescence sensor with high sensitivity,high selectivity,and high recyclability. |
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