Preparation And Application Of Porous Organic Frameworks Composites In Electrochemical Sensing

Covalent organic frameworks(COFs)and metal organic frameworks(MOFs)are a class of porous crystalline materials that have attracted a great deal of attention.Among them,COFs are assembled by covalently bonding light elements such as O,B,N,and C with organic ligands,which possess excellent stability,low weight density,and flexibility.MOFs,on the other hand,are assembled by metal ions or metal-containing clusters as secondary building blocks with organic ligands in coordination,which are characterized by tunable morphology,conformational diversity,and precisely controllable pore environment.However,COFs or MOFs have their own disadvantages such as weak conductivity and poor catalytic performance,which hinder their development in the direction of electrochemical sensing.In this context,composite materials based on COFs or MOFs have been widely studied due to their excellent chemical properties.In this thesis,we aim to improve the electrical conductivity and catalytic activity of materials,prepare composites based on COFs or MOFs as substrates,and construct a series of electrochemical sensors to carry out the following work:Chapter 1 Synthesis of core-shell structured metal oxide@covalent organic framework composites as a novel electrochemical platform for dopamine sensingA novel core-shell structured CuO@TAPB-DMTP-COF composites were synthesized by encapsulating CuO nanorods into TAPB-DMTP-COF host matrix.After performing different structural characterization tests,CuO@TAPB-DMTP-COF composites were immobilized on the surface of glassy carbon electrode(GCE)to prepare an electrochemical sensor for dopamine detection.CuO functions as a highly catalytic active substance to accelerate the charge transfer rate of the reaction,while TAPB-DMTP-COF with a large electroactive surface area enhances the adsorption ability of dopamine.The main parameters during the analytical procedure were investigated in detail,and the analytical performance was improved significantly due to the synergistic effects of CuO and TAPB-DMTP-COF.Under the optimal conditions,the dopamine peak responses are linear in a wide range from 0.07-800 μM,and the detection limit is as low as 0.023 μM.Furthermore,the dopamine sensor also exhibits good stability,repeatability and accurate detection ability in actual samples.This work will expand the application of COFs in ultra-sensitive electrochemical bioanalysis.Chapter 2 Integration modification of hollow metal organic frameworks by enzymes and Au nanoparticles for electrochemical BHA biosensorHollow metal organic frameworks(HMOFs)as hosting material with conducting and enzyme catalytic properties are a promising potential for electrochemical biosensor.Here,horse radish peroxidase(HRP)was immobilized into zeolite imidazolate framework-8(ZIF-8)with a co-precipitation way.After etching with tannic acid,a novel hybrid porous HRP@HZIF(HZIF stands for hollow ZIF-8)nanocomposite was prepared.Further functionalization of Au NPs was obtained using the reduction method.The resultant HRP@HZIF-Au electrochemical biosensor demonstrated a highly electrocatalytic activity for the determination of butylated hydroxy anisole(BHA)with an extended linear detection range from 0.001-900 μM and low detection limit of 0.34 nM.It seems that the remarkable catalytic efficiency of HRP@HZIF-Au for BHA may result from synergistic effects of hollow ZIF-8,HRP and Au nanoparticles.Meanwhile,the HRP@HZIF-Au nanocomposite was even stable against strong acids and organic solvents.The present work constitutes a significant advance in the hollow MOF-based electrochemical biosensor.Chapter 3 Construction of Core-Shell MOF(Fe/Cu)OT@COF as an excellent electrochemical platform for 2,4,6-trichlorophenol detectionThe widespread use of pesticides requires effective detection and quantification tools to improve the monitoring of environmental quality.In this work,an electrochemical sensor for the determination of 2,4,6-trichlorophenol(TCP)was successfully achieved.MOF(Fe/Cu)was prepared by the solvothermal method,and MOF(Fe/Cu)DT@COF were abtained by grafting COF onto MOF using a Schiff base condensation reaction with monomer-initiated in situ polymerization for electrode materials in electrochemical sensors using MOF(Fe/Cu)as the nucleus.Cyclic voltammetry and differential pulse voltammetry techniques were applied to study the electrochemical behavior of the developed sensors.Under the optimal conditions,the linear range of TCP was found to be 0.01-10 and 10-900 μM,and the detection limit of 0.003 μM.In addition,the content of TCP in school ponds and tap water was measured with the recovery of 98.7-103.2%,which proved the practicality of the prepared sensor.