Design,Synthesis And Sensing Properties Study Of Lanthanide Metal-Organic Frameworks Materials

Metal-organic frameworks(MOFs)are an emerging and rapidly developing class of porous and crystalline materials consisting of metal ion/cluster nodes or secondary building units(SBUs)and organic linkers through coordination bonds.MOFs have demonstrated great potential in adsorption,gas storage/separation,proton conduction,catalysis,drug delivery and fluorescence sensing.Thereinto,lanthanide metal-organic frameworks(Ln-MOFs)with the excellent photoluminescent properties through an“antenna effect”are promising chemical sensing materials.Up to now,luminescent Ln-MOFs have shown recognition abilities for cations,anions,organic small molecules,gases,nitro explosives,and so on.However,most of reported Ln-MOFs still suffer from some obvious drawbacks,such as the weak water-stability.Secondly,the accuracy of sensor based on MOFs with one emission may be affected by the external environment factors.Furthermore,MOFs typically formed as microcrystalline powders greatly limit the operation for industrial scale applications.In this dissertation,to overcome the above problems,different series of water-stable Ln-MOFs have been successfully constructed by an effective strategy of selecting purposeful ligands.Secondly,we doped with different lanthanide ions into its frameworks to obtain dual-emission Ln-MOFs and prepared as a ratiometric fluorescent sensor.In addition,the novel Ln-MOF mixed-matrix membrane by combining water-stable MOF with agarose were further prepared under environmentally friendly and simple operating conditions,which exhibits the sensing nature and integrity of Ln-MOF powder.1.Two three-dimensional porous structures Ln-MOFs(termed as Eu-MOF and Tb-MOF)were successfully constructed by the strategy of anchoring Eu³⁺/Tb³⁺,rigid1,2,4,5-benzenetetracarboxylic acid(H₄BTEC)and imidazole units(H₃ICA)onto its frameworks.The obtained Eu-MOF and Tb-MOF display high water stability,acid-basic stability and thermal stability.Furthermore,luminescent studies reveal that Eu-MOF and Tb-MOF show rapid sensing of Fe³⁺and Cr₂O₇^2-/Cr O₄^2-ions in water.In addition,Eu-MOF and Tb-MOF have excellent cyclability and selectivity.2.A water-stable terbium metal-organic framework(Tb-MOF-A)and a near-infrared-emissive lanthanide metal-organic frameworks(Nd-MOF-Y)were fabricated by 1,10-phenanthroline(Phen),2,3,5,6-tetrafluoroterephthalic acid(H₂tftba)and Tb³⁺/Nd³⁺under hydrothermal conditions.Due to the features of the pyridine and fluorine-functionalized organic ligands and Ln³⁺ions,Tb-MOF-A can quickly,quantitatively and circularly detect Cr₂O₇^2-anions and Fe³⁺cations in water and picric acid(PA)in a simulated seawater environment.Nd-MOF-Y exhibits the near-infrared-II emission characteristics and Nd-MOF-Y can detect cyclotetramethylene tetranitramine with high sensitivity,selectivity,cyclicality,and low detection limit.In addition,the stability studies exhibit that Tb-MOF-A and Nd-MOF-Y have excellent water stability,acid-basic stability,thermal stability.3.A dual-emitting lanthanide metal-organic framework(Eu_0.07Gd_0.03-MOF)based on functionalized ligands was prepared,which can be developed as a ratiometric sensor.The stability surveys indicate that Eu_0.07Gd_0.03-MOF have excellent water stability,acid-basic stability,thermal stability.More importantly,this self-calibrated material offers the highly sensitive and color-change detection method of Fe³⁺and ascorbic acid,the low concentration range of Fe³⁺and ascorbic acid can be estimated by the ratios of ligand-based emission as an internal reference and Eu³⁺-based emission as the indicator,which gives a visually discernible“color-change-recover”effect.4.A water-stable metal organic frameworks,[Eu(Phen)₂·(L-Cl4)_1.5·H₂O](CUST-506).(L-Cl4=2,3,5,6-tetrachloroterephthalic acid,Phen=1,10-phenanthroline)has been synthesized and characterized.By immobilizing water-stable CUST-506 into agarose hydrogels,the Eu-MOF mixed-matrix membrane was successfully prepared.The Eu-MOF mixed-matrix membrane exhibits not only the integrity and metronidazole,picric acid(PA)sensing nature of Eu-MOF powder,but also excellent processability Moreover,the Eu-MOF mixed-matrix membrane shows distinguished water-stability.More interestingly,during the hydrothermal synthesis process,by introducing the formic acid as a terminal ligandtobuildonedimensionalcompound{[Eu(Phen)·(L-Cl4)_0.5(COOH)·2H₂O]·(L-Cl4)_0.5}(CUST-507)with two emission centers from Eu³⁺based centers and free L-Cl4 molecules.CUST-507 displays unique advantage of self-calibration based on their dual-emitting mechanism and sensitive sensing detection of metronidazole and picric acid.