| Due to the needs of environmental monitoring and national defense security,the importance of rapid,stable,efficient,and convenientat sensing some kinds of cations,anions,and nitroaromatic compounds a trace level has been increasingly emphasized.Metal-organic frameworks(MOFs)as an emerging class of crystalline porous materials that constructed by inorganic metals and organic ligands have abundant light-emitting sites,adjustable light-emitting range and various pore structures.They have been successfully applied in the fields of fluorescence detection,light-emitting devices and biological imaging.However,most of the luminescent MOFs explored so far have poor water stability,making it difficult to cope with complex and relatively harsh detection systems,and most MOFs are still limited to single-emitting fluorescent sensing signals,which makes detection results difficult to achieve higher accuracy and precision.In this work,a highly stable fluorescent MOF material is prepared by combining a fluorescent ligand with a zirconium-based metal.On this basis,a fluorescent MOF composite with self-calibration properties is prepared by loading a fluorescent dye.Then,the luminescent characteristics of two kinds of luminescent MOF and their performance and detection mechanism in the rapid detection of inorganic ions and nitroaromatic compounds were compared,which provided experimental accumulation for the development and utilization of new fluorescent MOF materials.The main works are summarized as follow:(1)A blue fluorescent zirconium-based MOF compound was prepared by solvothermal method using blue fluorescent 4,4’-stilbene dicarboxylic acid as organic ligand and zirconium tetrachloride as metal salt.It is a cage compound having a fcu topology formed by the interpenetrated of a 12-connecting 6-nuclear zirconium metal cluster to a ligand.The fluorescence spectrum shows that when the excitation wavelength is 365 nm,the maximum emission peak of the zirconium-based MOF compound is 455 nm,which corresponds to blue emission.As a fluorescent sensing material,the compound exhibits a highly selective fluorescence quenching response to Fe3+ in the cation,Cr2O72-in the anion,and 2-nitrophenol in the nitroaromatic compounds.The Stern-Volmer(SV)plots of Fe3+and Cr2O72-are linear in a wide concentration range,and the value of the quenching constants Ksv are 7.00 × 103 M-1 and 6.26 × 104 M-1,respectively.The SV plots of 2-NP has a linear relationship only in the low concentration range,and the value of the quenching constants KSv is 3.50 × 103 M-1.It is indicated that the zirconium-based MOF compound can be used as a fluorescent sensing material to detect inorganic ions and nitroaromatic compounds.(2)A fluorescent MOF-based compound has been synthesized by incorporating a fluorescent dye Eosin Y(EY)into the zirconium-based metal-organic frameworks through a in-situ synthetic encapsulation method and the as-synthesized compound also exhibits porosity while retaining the original zirconium-based MOF structure.The compound presents a dual-emitting luminescent property,which shows a weak emission based on MOF host centered at 446 nm and a strong emission based on guest EY molecule centered at 553 nm when excited at 365 nm.The compound exhibits uniformity of luminescent characteristics in a variety of solvents.In view of this situation,the compound can be used for detecting cations and anions in the aqueous solution and nitroaromatic compounds in the ethanol solution,where the emission peak of the MOF host serves as a reference peak to calibrate the emission peak of the EY molecule by measuring the relative peak height of both emissions replace absolute peak height.The compound exhibits a highly selective fluorescence quenching response to Fe3+in the cation,Cr2O72-in the anion,and 2-nitrophenol in the nitroaromatic compounds.The SV plots of Fe3+,Cr2O72-and 2-NP are linear in a broad concentration range,and the value of the quenching constants Ksv is 1.02 × 104M-1 1.44 × 105M-1 and 1.33 × 104M-1,respectively. |
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