Preparation And Electrocatalytic Applications Of Metal Organic Polymers

Metal Organic Frameworks（MOFs）are a novel metal-organic polymercomposed of metal/metal cluster（such as Mn,Fe,Co,Ni,etc.）and Organic ligands（such as containing heteroatom N and O,etc.）.MOFs are a porous crystal material.MOFs and their derived nanomaterials have made important application progress in many technical fields in the past decade due to its high specific surface area,regulated structure and composition as well as pore channels.In present work,novel MOFs and their derived nano-materials using transition metal（copper,cobalt）and organic ligand as raw materials were prepared,chiral electrochemical sensing and oxygen evolution reaction（OER）in water splitting of these composites were studied.The main contents include the following four aspects:1、Using L-Asp,grapheme and copper nitrate as main raw materials,graphene functionalized Cu-MOFs/GO composites were successfully prepared at room temperature.The crystal structure,chemical composition and surface morphology of the composites were characterized by SEM,XRD and IR spectroscopy.It was confirmed that the material is a chiral MOF material.In order to clarify the sensing behavior of the synthesized composite material,the sensing potential,current density and impedance of the material were determined by electrochemical methods such as DPV,CV and EIS.The effects of various factors on the sensing properties of synthetic composites were studied including the pH of buffer solution.Histidine enantiomers were selected to be recognized.The differential pulse voltammetry was used to successfully identify the L-/D-histidine.2、A new type of chiral Cu-MOF crystal was prepared using copper nitrate and L-Asp as raw materials.The crystal structure was confirmed to be[Cu（Asp）]·2H₂O（Cu-Asp）by single crystal diffraction.The in-situ growth of[Cu（Asp）]·2H₂O nanofibers on Cu Foam（CuF）was realized by anodization oxidation electrodeposition method.The crystal structure of ontained Cu-Asp/CuF by optical microscopy,SEM and XRD was characterized.The Cu-Asp was confirmed to be chiral by circular dichroism.By means of differential pulse voltammetry and other detection methods,the chiral recognition of Cu-Asp/CuF to histidine enantiomers was carried out.3、Using 1,4,5,8-naphthalene tetracarboxylic anhydride and copper nitrate as main raw materials,a new Cu-MOF was prepared at room temperature.The structure[Cu（NTA）₂（DMF）（H₂O）]n was determined by single crystal diffraction,belonging to the triclinic system,P-1 space group.The asymmetric unit of the complex includes two Cu（II）ions,two ligand anions,two coordination water molecules and two coordination DMF molecules.An integrated electrochemical sensor（Cu-MOF/CuF）was prepared by electrodeposition,in which nanosheet arrayof Cu-MOF was loaded on foam Cu.Compared with pure Cu-MOFs electrode,Cu-MOF/CuF shows excellent catalytic effect in electrocatalytic oxygen evolution.The Tafel slope of 125 mV dec^-11 was satisfactory due to its high specific surface area and porosity of Cu-MOF/CuF.4、A new MOF/CoF composite functionalized by carbon dots（CDs）was prepared and used to electrochemical oxygen evolution in water splitting.The glucose was used to prpare CDs by microwave method.CDs functionalized composites（CDs-Co₃O₄-CN/CoF）were prepared using triethylene diamine（TED）and terephthalic acid（H2bdc）as mixed ligands by Co plate potentiostatic oxidation electrodeposition,which was further pyrolyzed.The crystal structure,chemical composition and surface morphology of the composites were characterized by SEM,XRD,infrared spectroscopy and XPS.The optical properties were detected by UV and fluorescence spectroscopy.The oxygen evolution overpotential,current density and impedance of the material were determined by LSV,CV,I-t curve and EIS to clarify the oxygen evolution behavior.The effects of various factors on the oxygen evolution performance of synthetic composites,including activation and pyrolysis methods and time,material composition,etc.,were investigated.The oxygen evolution activity of various materials was evaluated by LSV.When CD-MOF/CoF was pyrolyzed at 300°C for 2h,the optimized composite Co₃O₄-CN/CoF was obtained.The excellent oxygen evolution reaction activity with alow overpotential in 1.0 M KOH and long-playing durability in oxygen evolutioncan be ascribed to its highly dispersed Co₃O₄ nanocrystals,CQDs and nitrogen codoping,internal cavities,andhierarchical pore system.