Synthesis Of Metal-Organic Framework Composites And The Applications In Electrochemical Sensors

Electrochemical analysis is a commonly used detection method in analytical de-tection,which has the advantages of high sensitivity,low detection limit,fast response and portable equipment.It has various detection methods and can be analyzed using various data such as current,potential,electrochemical impedance,etc.The perfor-mance of electrochemical sensors can be improved by selecting modification materials with different functions.Therefore,the synthesis of new modification materials is the primary research direction in the field of electrochemical sensors.Metal-organic framework materials（MOFs）are formed by the coordination of central metals and organic ligands in three-dimensional（3D）space.MOFs have a peri-odic skeleton structure,high porosity,and large specific surface area.Once discovered,MOFs have attracted the attention of researchers and have developed promptly.MOFs have been mostly applied in gas storage and separation,energy storage and conversion,catalysis,sensors,and other fields.However,the boundary orbitals of MOFs have poor overlap with electrons on ligands or metal ions,making them commonly considered as low conductivity materials.Moreover,the poor water stability and low mechanical strength of some MOFs limit the direct application of pure MOFs as modified electrode materials.In the field of electrochemical analysis,we can improve the conductivity and catalytic properties of MOFs by changing the composition of the central metal,selecting organic ligands with different functions,and optimizing crystal morphology.On the other hand,in order to improve the electron transfer ability and electrochemical sensing performance of MOFs,we can be combined with materials with high conduc-tivity,strong catalytic activity and stable structure,such as carbon-based materials,metal nanoparticles（MNPs）,metal compounds and polymers.In addition,MOFs can also be used as self-sacrificial templates to synthesize carbon-doped materials or lay-ered double hydroxides（LDH）,so that the metal active sites hidden in the MOFs frame-work can be fully exposed to improve the electrocatalytic performance and enhance the electrochemical signal.The above methods are conducive to enhancing the sensitivity,stability,and detection ability of electrochemical sensors,effectively improving the per-formance of electrochemical sensors.Therefore,this paper studies MOFs composites and constructs electrochemical sensors for the analysis and detection of hydrogen per-oxide,dopamine,estradiol,and trimetazidine.The specific work is as follows:1.Hierarchical heterogeneity bimetallic CuCo-BDC/GO was synthesized by a straightforward one-pot solvothermal reaction.The prepared materials can be exploited for constructing an electrochemical biosensor for H₂O₂ sensing with peroxidase-like activity.The hierarchical heterogeneity bimetal-organic nanostructures CuCo-BDC/GO have numerous open metal active sites,synergistic effect based on bimetallic centers,hierarchical structure with high specific surface areas and outstanding electrochemical properties of GO.The electrochemical sensor based on CuCo-BDC/GO has good cata-lytic activity for the reduction of H₂O₂.It’s also suitable for the detection of H₂O₂ in human serum.Therefore,this research can promote further exploration about the detec-tion of reactive oxygen species using mixed-metal MOFs.2.Porous bimetallic nickel-cobalt layered double hydroxide（NiCo-LDH）was synthesized in situ through a one-step solvothermal reaction using ZIF-67 as self-sac-rificial template.NiCo-LDH using ZIF-67 as a self-sacrificial template has better dis-persibility and is less prone to aggregation.The reduction of graphene oxide（GO）to reduced graphene oxide（rGO）using electrochemical methods can be used as a platform for signal amplification.Due to the bimetallic synergistic effect of Ni and Co,large specific surface area,numerous catalytic active sites and strong electrical conductivity high conductivity,rGO/NiCo-LDH can be application to the recognition of DA by elec-trochemical methods.The electrochemical sensor based on rGO/NiCo-LDH has high sensitivity and stability,and also be suitable for detecting DA in human serum.3.The composite Cu CATs/PdPt is composed of bimetallic PdPt nanospheres pre-pared by one-step reduction and Cu CATs,a conductive MOFs synthesized by sol-vothermal method.The strong charge delocalistion between the Cu active center and the ligand（HHTP）based on MOFs and the large specific surface area of Cu CATs/PdPt accelerate the mass transfer speed and enhance the conductivity of the composite.Be-cause of the synergistic effect of bimetal,the catalytic property of PdPt nanospheres is higher,and the high conductivity of PdPt nanospheres can also serve as a platform for electrochemical signal amplification.Therefore,Cu CATs/PdPt can be used as a sensing platform for non-enzymatic electrochemical detection of estradiol,with promising ap-plications in the fields of biosensing and environmental monitoring.4.Nano-sized CdS/MOF-74T composite by shape optimization was synthesized by solvothermal transformation strategy to enhance the detection capability for TMZ.To optimize the morphology of CdS/MOF-74T,the experiment starts from the follow-ing aspects:synthesis of controllable morphology nano-sized intermediate ZIF-67;low concentration ligand solution used in solvothermal transformation;agglomerate these tiny MOF-74T particles onto rod-shaped CdS to prevent tiny MOF-74T particles ag-gregation.Shape-optimized nanosized CdS/MOF-74T composite showed better elec-trocatalytic activities,electrochemical stability,exposing more active sites and reducing mass transfer resistance,which is conducive to the diffusion of reactants.The CdS/MOF-74T electrochemical sensor has high sensitivity and selectivity for TMZ de-tection,and can be used for ultrasensitive detection of TMZ in human urine samples.