Preparation Of Redox Metal-organic Frameworks Composites As Electrodes For Electrochemical Energy Storage

Supercapacitors,as a type of reliable and practical energy storage devices,have exhibited the advantages of high power density,fast charge/discharge speed,and long cycle life.Current research hotspot focuses on seeking an electrode material with high energy density and good stability.Metal-organic frameworks（MOFs）as a porous crystalline material have advantages such as customizable pore structure,large specific surface area and functionalized functional groups,which has caused extensive research in the field of energy storage.However,poor conductivity and low specific capacity limited further application in supercapacitors.Post-synthetic modification（PSM）of MOFs are emerging as hybrid combining the unique features of the individual components to enable the generation of materials displaying novel physicochemical properties,which provides the possibility for the further application of MOFs in the field of energy storage.Based on this,we modified small quinone molecules to the surface of MOFs through azo bonds by post-synthesis modification,and combined with carbon nanotubes and polyaniline two different materials,and studied their application in supercapacitors.The specific research content is as follows:（1）In chapter two,we first synthesized a kind of azo bond redox metal organic frameworks（MOFs）,which were supported in situ on single-walled carbon nanotubes（CNTs）,further filtered to prepare non-woven flexible membrane electrodes The in situ guided growth,crystallinity and morphology of Ui O-66-NO₂ MOFs were finely controlled in the presence of CNTs.The MOFs’covalent anchoring to CNTs and solvothermal grafting anthraquinone（AQ）pendants endow the hybrid,denoted as CNT@Ui O-66-AQ,with greatly improved conductivity,charge storage pathway and electrochemical dynamics.At 1 m A cm^-2,the flexible CNT@Ui O-66-AQ displays a highest area specific capacitance of 302.3 m F cm^-2 in-0.4～0.9 V potential window,together with 100%capacitance retention over 5000 cycles at 5 m A cm^-2.Its assembled symmetrical supercapacitor（SSC）achieves a maximum energy density of0.037 m Wh cm^-2 and a maximum power density of 10.4 m W cm^-2,outperforming many MOFs hybrids based SSC in the literature.Our work may open a new avenue for preparing azo-coupled redox MOFs hybrids with carbaneous substrates for high-performance robust aqueous energy storage.（2）In chapter three,metal-organic frameworks MOF-2 containing two modifiers was further prepared by a simple hydrothermal reaction,and then a hydrothermal reaction was used agian to prepare an naphthoquinone modified redox metal organic framework MOF-2-NQ,finanly chemical polymerization with aniline,MOF-2-NQ@PANI electrode is synthesized.MOF-2-NQ@PANI displays a highest specific capacitance of 719 F g^-1 at 1 A g^-1,which is about 200 F g^-1 higher than MOF-2@PANI,and four times higher than MOF@PANI electrode,The capacitance retention was 62.6%when current density was increased to 20 A g^-1,the specific capacitance retention rate is as high as 62.6%.In addition,its assembled hybrid supercapacitor（HSC）achieves an ultra-high power density of 10 k W kg^-1.Overall,in this paper,we have designed redox MOFs and incorporated them with CNTs or conductive polymers to prepared high energy storage performance electrodes.Through the assembly of supercapacitors and researsh energy storage mechanism of,we have revealed the application prospects of designing redox MOFs composite electrodes in electrochemical energy storage,and provided certain guidance value for the application of supercapacitors.