Synthesis Of Functionalized Metal-organic Framework Materials And Their Applications In Optical Sensing And Enzymatic Catalysis

Metal-organic frameworks(MOFs)are ideal excellent candidates for chemical sensing and mimic enzyme materials due to their excellent structure,remarkable fluorescence properties,modifiable properties,etc.Various MOFs can be functionalized to provide desired host-guest interactions.In this thesis,functionalized MOFs with different substances(organic dyes,metal nanoclusters,metal ions and metal nanoparticles),are used as research objects,and investigated their fluorescence enhancement properties and simulated enzyme catalytic performance.Then these materials are respectively used to optically sense the alcohols solvents' polarity,ions,biomolecules,enzyme activity and the degradation of nerve agent simulant.At the same time,the interaction mechanism between functionalized MOFs composite materials/system and target is also deeply explored.The main research contents of this thesis are as follows:(1)The surface adsorption constraint provided by UiO-66 controls the movement of the fluorescent molecular rotor dye ThT,and the fluorescence of ThT is enhanced.By changing the functional groups on the surface of UiO-66,UiO-66 derivatives with different hydrophilicity,hydrophobicity and polarity are obtained.After ThT was adsorbed by MOFs,the micro-environmental factors of ThT fluorescence enhancement were studied.In addition,the fluorescence enhancement law of UiO-66+ThT in alcohol solvents with different polarities was investigated.This work provides a simple,rapid and inexpensive method for the fluorescence enhancement of MOFs+dyes.It also explores the influence of the hydrophobicity,interface polarity and environmental polarity of MOFs materials on the luminescence of the MOFs+ThT system,and provides new ideas for understanding the relationship between the luminescence phenomenon of ThTand the physical environment in the process of protein fibrosis.(2)Both UiO-66+ThT and Zr-NDC+ThT have fluorescence resonance energy transfer(FRET)phenomenon,which is conducive to the transfer of fluorescence signals from the short wavelength of MOFs to the long wavelength of ThT.Zr-NDC not only provides the conditions for ThT fluorescence enhancement,but also provides specific recognition of the target PO43-.Based on the FRET phenomenon of Zr-NDC and ThT,a new ratio fluorescence platform was established for PO43-sensing.As the concentration of PO43-increased from 0.2 ?M to 150 ?M,the fluorescence intensity of Zr-NDC+ThT system changed proportionally,and the detection limit was 0.09 ?M.The material is cheap and easy to obtain,easy-to-synthesize,and the ratio sensing mode provides a built-in correction function.This method has high sensitivity,wide detection range,good selectivity,and has broad prospects in environmental water monitoring and other fields.(3)A fluorescence analysis method based on gold nanoclusters(AuNCs)and metal-organic frameworks(MOFs)composite materials(AuNCs@ZIF-8)was established for highly sensitive detection of bilirubin(BR).First,AuNCs@ZIF-8 was successfully obtained by co-precipitation and displayed aggregation-induced emission enhancement by the confinement effect of MOFs(i.e.,ZIF-8).The product showed approximately 7.0 times enhancement in the quantum yield and longer fluorescence lifetime from 2.29 ?s to 11.51 ?s compared with AuNCs.BR combined with the metal node Zn2+of ZIF-8,and the skeleton of the composite was destroyed,leading to great decrease in the fluorescence intensity by the transformation of AuNCs from the aggregation state to the dispersed state.The linear range for the detection of BR was 0.1-5.0 ?M,with the limit of detection(LOD)of 0.07 ?M(S/N=3).AuNCs@ZIF-8 exhibited selectivity response toward BR within 5 min and detected BR in human serum.The long-wavelength emission by AuNCs avoided the interference of the complex biomatrix background fluorescence,indicating their great application prospects for clinical diagnosis.(4)Fe(?)functionalized PCN-222 has the properties of peroxidase-like activity.A colorimetric detection method for acetylcholinesterase(AChE)activity and inhibition is developed using metal organic frameworks(MOFs,i.e.,PCN-222(Fe)).PCN-222(Fe)can catalyze the reaction of colorless 3,3',5,5'-tetramethylbenzidine(TMB)with H2O2 into oxidized TMB(oxTMB)with an absorption peak at 652 nm to generate a blue color.AChE can catalyze the hydrolysis of acetylthiocholine chloride to produce thiocholine(TCh).The blue color fades,and the absorbance decreases due to the reduction of oxTMB by the produced TCh.The detection platform shows sensitive responses to AChE with a linear range of 0.05-10 mU mL-1 and a low detection limit of 0.03 mU mL-1.In the presence of the AChE inhibitor,the production of TCh from the catalytic reaction is retarded,and the blue color does not fade.The linear range of paraoxon detection is 0.25-2.5 ng mL-1,and the detection limit is 0.2 ng mL-1.Thus,the developed simple and sensitive colorimetric sensing strategy could enhance the application of MOFs.(5)Organophosphate(OP)are highly toxic and widely used as pesticides and chemical nerve agents.In this work,a facile approach for cascade degradation of OPs nerve agent simulants is established via a hybrid material,which is prepared by growth of Pd nanoparticles(PdNPs)in metal-organic frameworks(MOFs)(PdNPs@PCN-224)(PCN=porous coordination network).PCN-224 acts not only as the support material but also as an effective enzyme mimic of organophosphorus hydrolysis(OPH),which can completely degrade paraoxon,the model OP compounds,into p-nitrophenol(p-NP).Thereafter,the degraded product(p-NP)with moderate toxicity is further efficiently reduced into p-aminophenol(p-AP)with less toxicity by NaBH4 under the catalyzation of PdNPs.This work displays a great potential to construct highly bifunctional catalysts by integrating the merits of artificial enzymes and metal NP catalysts,which are promising for applications in the successive degradation of OP nerve agents.