Preparation Of Several Covalent Organic Framework Composite Materials And Their Electrochemical Sensing Applications

Covalent organic frameworks（COFs）are a kind of crystilline organic porous polymers covalently connected by light elements such as B,H,C,N,O,and Si.Because of their high specific surface area,regular pore structure,good crystallinity and high chemical stability,COFs have shown great application potentials in many fields including chemical sensing,energy storage,gas storage and separation,photocatalysis and drug delivery and become a research hotspot in recent years.However,the poor conductivity of COFs limits their applications as an electrode material in electrochemistry.Therefore,in this thesis,1,3,5-tris（4-formylphenyl）benzene（TFPB）,which has a large conjugatepbond structure,is selected as a basic structural block to synthesize conductive COFs through Schiff base reaction.Through composition with other well-conductive materials,some eletrochemical sensors with excellent perofrmances are expected to construct.The thesis mainly includes three parts as follows:1.Using TFPB and 1,4-p-phenylenediamine（PDA）as monomers,imino bond linked COF-1（TFPB-PDA-COF）was synthesized by Schiff base reaction,and then a novel electrochemical sensor COFs/NH₂-r G/MoS₂/GCE was successfully fabricated by employing the prepared COFs with amino-functionalized graphene and MoS₂nanosheets as modified materials.The sensor displayed sensitive electrochemical responses to guanine（GU）and adenine（AD）and could be exploited to determine these two analytes simultaneously and repidly with wide linear ranges（GU:0.5-150μM,AD:1-280μM）and low detection limits（LODs）（GU:0.51μM and AD:0.44μM）.And the developed analytical procedure has been successfully used for determination of GU and AD in heat-denatured salmon sperm DNA with satisfactory results.2.Magnetic COF-2（Fe₃O₄@TFPB-DAAQ-COF）was synthesized by using TFPB and 2,6-diaminoanthraquinone（DAAQ）as monomers in the presence of Fe₃O₄nanoparticles,and an electrochemical sensor with excellent electrochemical properties was constructed with the obtained COFs,Au NPs and MoS₂ as composition modified materials.The developed sensor possessed a high electrocatalytic activity forward the electrochemical oxidation of Quercetin（QU）and could be employed to determine the target molecule in red wine sample with a high sensitivity and a good selectivity.3.Au-Pt NPs supported COFs（Au-Pt NPs-COF）were successfully prepared with TFPB and melamine（MA）as monomers in the presence of bimetallic Au-Pt NPs.And then a sensitive electrochemical sensor Au-Pt NPs-COFs/GCE for acetaminophen（AMP）and dopamine（DA）was constructed by a simple drop coating method.The prepared composition materials possessed not only good conductivity but also outstanding electrocatalytic activity,as a result,the fabricated sensor showed wide linear ranges（AMP:0.5-30 and 30-330μM;DA:0.1-10 and 10-190μM）and low LODs（AMP:0.21μM and DA:0.083μM）.In addition,the proposed method was also used to determine the contents of these two analytes in commercially available medicines rapidly,sensitively and actuately.