Synthesis And Fluorescence Properties Of Functionalized Zirconium-based Metal-Organic Framework

Since the 21st century,metal-organic frameworks(MOFs)built by the coordination of organic ligands and metal ions or clusters have attracted much interest due to their structural diversity,adjustable pore size,large surface area,high porosity and potential applications in different areas.UiO-66-NH2(UiO=University of Oslo)is a three-dimensional rigid MOF material composed of zirconium-oxide clusters as the metal center and 2-Aminoterephthalic acid as the organic ligand.It is one of MOFs materials applied widely with high hydrothermal,chemical and mechanical stability.In this thesis,our interest was focused on the size-controllable synthesis of UiO-66-NH2 nanocrystals,the functional modification of the MOFs’ framework and the fluorescence detection.The main contents are as follows:1.UiO-66-NH2 microspheres with-50 nm in size were synthesized by a one-step solvothermal method in N,N-dimethylformamide solvent,using zirconium tetrachloride as the metal source and 2-Aminoterephthalic acid as the organic ligand in the presences of the mediation of acetic acid and water at 120℃ for 24 h.The fluorescence tests showed that under the ultraviolet light excitation of 344 nm,UiO-66NH2 microspheres emit a blue-violet light centered at 425 nm.Further experiments uncovered that the color of the final product changed from pale yellow to orange-red after UiO-66-NH2 microspheres were modified with Calcein;and simultaneously,the fluorescence at 425 nm was quenched.After introducing Ca2+ions,however,the above fluorescence was recovered.This phenomenon was not interefered from some common amino acids and various ions,implying that the as-synthesized UiO-66-NH2@Calcein could be used as a probe for detection of Ca2+ ions in aqueous systems with a rapid response of 300 s.Also,the present probe had good linearity in the region of 0-10 μM with the detection limit as low as 0.6 μM.The present work provides a new approach for the visualized detection of Ca2+ions in the living cell.2.UiO-66-NH2 with uniform morphology and good crystallinity was successfully synthesized in aqueous phase,employing trifluoroacetic acid and formic acid as regulators,zirconium oxychloride as metal source,2-Aminoterephthalic acid as the organic ligand at 120℃ for 24 h.Then,the as-synthesized UiO-66-NH2 was postmodified with taurine in the presence of a condensing agent for 24 h at room temperature to obtain UiO-66-NH-Taurine.The fluorescence of UiO-66-NH2 was quenched owing to the modification of the amino groups.The study showed that merely repaglinide could turn on the above quenched fluorescence without the interferences from other drugs and amino acids,suggesting that the present probe owned excellent selectivity and anti-interference ability for detection of repaglinide.In the region of 0120 ng/mL,a good linear relation was obtained and the detection limit was as low as 10.2 nM(4.61 ng/mL).These experimental results indicated that UiO-66-NH-Taurine could be used as a selective recognition probe for repaglinide in aqueous system.3.Yellow UiO-66-N=CH-C4H3S was successfully prepared in a round-bottom flask at 80℃ for 24 h via a refluxing route,employing yellowish UiO-66-NH2 synthesized in the previous chapter and 3-thiophenecarbaldehyde as the reactants and ethanol as the solvent.The fluorescence properties showed that the fluorescence intensity of UiO-66-N=CH-C4H3S could be promoted by urea in aqueous solutions;and was not affected by some common substances including cations,anions,amino acids,antibiotics,and so on.The above facts indicated that the as-prepared UiO-66-N=CHC4H3S could be used as a fluorescent probe for selective detection of urea in water systems.The detection limit was as low as 3.85 μM.The present work provides a new probe selection for the fluorescent detection of urea in aqueous systems,which is of great significance in environmental and human health detection.