Enzyme-like Property And Related Application Of Iron-based Metal Organic Framework And Their Nanocomposites

With the advantages of high effeciency and strong specificity,natural enzyme has been important biocatalyst in living system.Nevertheless,natural enzyme tends to be easy-denaturation and high-cost,which restrains its widespread usage in practical life.Therefore,researchers have been devoted into exploiting stable and cheap enzyme alternative with same function,which was defined as enzyme mimetic.Iron oxide was considered as highly active enzyme-like catalyst.The metal nodes of iron-based metal organic frameworks with carboxylate ligand were iron-oxide clusters,which suggests iron-based metal organic framework was potential enzyme mimetic with high catalytic activity.In addition,metal organic framework has large specific surface area and high porosity,which is not only attractive in catalysis but also beneficial for dispersing nanozyme.On the basis,we prepared a series of iron-based metal organic frameworks and their nanocomposites,and evalutated their enzyme-like property,which were applied in dye-degradation system,luminol-based chemiluminescence system and TMB-based colorimetric system,This paper has included five chapters as follows.Chapter 1:The development of enzyme mimetics and metal organic framework?MOFs?was introduced in this section.Besides,the goal and content of research was given.Chapter 2:NH₂-MIL-88B?Fe?was prepared and used as a peroxidase-like catalyst for Fenton-like degradation of methylene blue?MB?in water.The iron-based NH₂-MIL-88B?Fe?MOFs was synthesized by a facile and rapid microwave heating method.It was characterized by scanning electron microscopy,Fourier transform infrared spectroscopy,powder X-ray diffraction,and the Brunauer-Emmett-Teller method.TheNH₂-MIL-88B?Fe?MOFpossessesintrinsicoxidase-likeand peroxidase-like activities,which can degrade MB efficiently.The reaction parameters of MB degradation were investigated,including the solution pH,NH₂-MIL-88B?Fe?MOF and H₂O₂ concentrations and temperature.The results show that the NH₂-MIL-88B?Fe?MOF exhibits a wide working pH range?pH 3.0-11.0?,temperature tolerance,and good recyclability for MB removal.Under the optimal conditions,complete removal of MB was achieved within 45 min.In addition,removal of MB was above 80%after five cycles,showing the good recyclability of NH₂-MIL-88B?Fe?.The NH₂-MIL-88B?Fe?MOF has the features of easy preparation,high efficiency,and good recyclability for MB removal in a wide pH range.Electron spin resonance and fluorescence probe results suggest the involvement of hydroxyl radicals in MB degradation.These findings provide new insight into the application of high-efficient MOF-based Fenton-like catalysts for water purification.Chapter 3:Sodium dodecyl benzene sulfonate modified MIL-88?Fe??SDBS@MIL-88?Fe??was prepared by microwave heating method.The peroxidase-like acitivity of SDBS@MIL-88?Fe?was investigated by H₂O₂-TMB colorimetric system.The result shows that the catatlytic activity of SDBS@MIL-88?Fe?after modification has been imporved into the twice of MIL-88?Fe?.Kinetic experiments shows that the apparent Michaelis constant of SDBS@MIL-88?Fe?with TMB as substrate was 0.21 mM which was lower than that of the reported iron-based MOF nanozymes,proving the good affinity between SDBS@MIL-88?Fe?and TMB.SEM images and DLS shows that SDBS can be conducive to the formation of small MOF crystals and good dispersity of MOF particles in water.These results suggest that the improved catalytic activity might be attributed to the enhanced density of negative charge,the formation of small crystals and good dispersity.Based on the peroxidase-like activity of SDBS@MIL-88?Fe?,a effective,sensitive detection method for H₂O₂ and glucose could be developed.This glucose detection method could be used in complicated samples like human serums.Chapter 4:GO@MIL-88?Fe?was synthetized through in-situ gowth of MOF crystal on graphene oxide,and characterized by SEM,XRD,FT-IR and Raman spectrum.In addition,the oxidase-like activity of GO@MIL-88?Fe?was evalutated by luminol-based chemiluminescence system.The results show that the introduction of GO could effectively enhance the oxidase-like activity of MIL-88?Fe?,the magnification could reach to 12.Based on the high active oxidase-like activity of GO@MIL-88?Fe?,a sensitive chemiluminescence method for ascorbic acid detection was proposed.The linear range was 1 nM-5?M,the dection of limit was 1 nM.This method could be applied in ascorbic acid detection of orange juice.This work was of great significance for application of MOF as oxidase mimetics.Chapter 5:CoFe₂O₄ NPs/GO@MIL-88?Fe?was prepared through diffusing CoFe₂O₄ NPs into the matrix GO@MIL-88?Fe?,and evaluated the peroxidase-like activity by luminol-H₂O₂ chemiluminescence system.The chemiluminescence signal for CoFe₂O₄ NPs/GO@MIL-88?Fe?is about 10 times of that for bare CoFe₂O₄ NPs.The high magnification is attributed to the dispersion of CoFe₂O₄ NPs on the MIL-88?Fe?and the robustness of MIL-88?Fe?stablized by GO.Based ont the high peroxidase-like activity of CoFe₂O₄ NPs/GO@MIL-88?Fe?,sensitive chemiluminescence methods for H₂O₂ and glucose detection could be realized.The detection of limit are 5 nM and 10nM,respectively.The proposed method for glucose detection could be applied in human serums with satisfactory result.