Design And Construction Of Stable MOFs And Their Applications In The Detection And Capture Of Environmenal Pollutants

In recent years,with the explosive growth of the population and the development of industry,the problem of environmental pollution has become one of the greatest challenges humanity is facing.Therefore,environmental protection and pollution control have attracted considerable public concern.The detection and removal of environmental pollutants play a key role in environmental protection and pollution control.Optical sensing and adsorption-based methods have been considered as promising technologies in the detection and removal of environmental pollutants because of many advantages,such as easy operation,energy saving,and high efficiency.As a class of newly developed organic-inorganic hybrid multi-functional materials,metal-organic frameworks（MOFs）are considered as a favorable platform for the detection/sensing and removal of environmental pollutants because of their unique electronic and optical properties,permanent porosities,high surface areas,and easily tailorable structures and functionalities.However,most MOFs suffer from poor chemical stability especially when exposed to water,limiting their applications in the areas mentioned above.Thus,the construction of stable MOFs for the detection and removal of environmental pollutions is of great significance.In this thesis,several highly stable MOFs have been constructed and used for the detection and removal of environmental pollutions,including antibiotics,aromatic nitro explosives,metal ions,and polychlorinated dibenzo-p-dioxins（PCDDs）.Corresponding results are summarized as follows:（1）Guided by a topological design approach,two stable isostructural Zr（IV）-based MOFs,BUT-12 and BUT-13 with the the-a topological structure have been designed and synthesized.The two MOFs are highly porous with the Brunauer-Emmett-Teller（BET）surface area of 3387 and 3948 m² g^-1,respectively.Interestingly,these MOFs represent excellent fluorescent properties,which can be efficiently quenched by trace amounts of antibiotics,like nitrofurazone（NZF）and nitrofurantoin（NFT）,as well as organic explosives,like 2,4,6-trinitrophenol（TNP）and 4-nitrophenol（4-NP）,in water solutions.The detection limits of BUT-12 toward NZF and TNP are 58 and 23 ppb;and those of BUT-13 are 90 and 10 ppb,respectively.Simultaneously,both MOFs also display high adsorption capacities toward these organic molecules.It has been demonstrated that the adsorption processes play an important role in the preconcentration of analytes,which can further increase the fluorescent quenching efficiency.These results indicate that BUT-12 and-13 are promising materials for the simultaneous selective detection and removal of specific antibiotics and organic explosives in water,being potentially useful in monitoring water quality and treating wastewater.（2）A stable Al（III）-MOF,BUT-22,with a soc-a topological framework structure has been constructed.BUT-22 has similar structure to Al-soc-MOF-1 and the difference between them is the presence of funcitonalized pyridine sites in the former.Based on the large surface area and good fluorescence property,the detection abilities of them toward veternary drgus have been explored.It was shown that the fluorescence of the two MOFs can be efficiently quenched by 15 commonly used veterinary drugs.Particularly,the quenching efficiencies of all these veterinary drugs by BUT-22 are all over 82%and the detection limit of BUT-22 toward NZF is 14 ppb.In addition,the two MOFs can selectively detect nicarbazin（NIC）veterinary drug through the red shift of their fluorescence emission spectra.The efficient fluorescent quenching effect is attributed to the combination of fluorescence resonance energy transfer,photoinduced electron transfer,the competition of excitation light energy between detected analytes and MOFs,and dynamic quenching process.（3）Two stable isostructural Zr（IV）-based MOFs,BUT-14 and BUT-15,with a sqc-a topological framework structures have been constructed for the detection of metal ions in water.Two new ligands utilized for the construction of the two MOFs,namely H₄BCQDA and H₄PBPTTBA,have similar structure with only difference being that the latter is functionalized by pyridine N atoms.The two MOFs are highly porous with the BET surface areas of 3595 and 3590 m² g^-1,respectively.Interestingly,the fluorescence of them can be solely quenched by trace amounts of Fe³⁺ions in aqueous solutions.The detection limits of BUT-14 and-15 towards the Fe³⁺ions are estimated to be 212 and 16 ppb,respectively.The efficient fluorescent quenching effect is attributed to the photoinduced electron transfer between Fe³⁺ions and the ligands in these MOFs.Moreover,the introduced pyridine N donors in the ligand of BUT-15additionally donate their lone-pair electrons to the Fe³⁺ions,leading to significantly enhanced detection ability.It has also been demonstrated that BUT-15 exhibits an uncompromised performance for the detection of Fe³⁺ions in a simulated biological system.（4）Two stable isostructural MOFs,BUT-16 and BUT-17,with csq-a topological structure have been constructed for the detection of PCDDs.The two MOFs are highly porous with the BET surface area of 1866 and 1790 m² g^-1,respectively.Interestingly,fluorescences of the two MOFs can be efficiently quenched by trace amounts of 2,3-dichlorodibenzo-p-dioxin（BCDD）,2,3,7,8-tetrachlorodibenzo-p-dioxin（TCDD）,and dibenzo-p-dioxin（DD）.The detection limits of BUT-16 towards BCDD and TCDD are estimated to be 182 and 215 ppb,and those of BUT-17 are 27 and 57 ppb,respectively.It is believed that the formation of nonfluorescent complex between the PCDDs and the ligands in BUT-17 throughπ-πstacking and hydrogen bonding interactions is the main mechanism of the fluorescent quenching.