Design,Synthesis And Electrochemical Performance Of Catechol-Bearing Conductive Metal-Organic Frameworks

Two-dimensional conductive metal-organic frameworks（2D c-MOFs）as an emerging class of multifunctional materials have attracted extensive attention due to their intrinsic permanent porosity,tunable structures,high charge mobility and excellent electrical conductivity.Such unique physicochemical characteristics render them as a promising new platform for electrochemical related devices.In this thesis,four types of new conjugated MOFs were successfully designed and constructed,meanwhile their structures,electrical properties and potential applications in the field of electrochemical energy storage and conversion were investigated.The main contents are summarized as follows:Firstly,a conductive copper（II）catecholate based metal-organic framework（denoted as Cu-DBC）was constructed using a non-planar 8OH-DBC（dibenzo[g,p]chrysen-2,3,6,7,10,11,14,15-octaol）ligand coordinated with Cu（OAc）2·H2O via solvothermal method.Cu-DBC exhibits high crystallinity,inherent porosity,good conductivity,and excellent redox reversibility.Cu-DBC was used as electrode material for supercapacitors,and further assembled a two-electrode solid-state symmetrical supercapacitor device.Benefiting from the combination of pseudocapacitance and electrochemical double-layer charge storage mechanisms,Cu-DBC electrode features not only superior gravimetric,areal,and volumetric capacitances,but also high power and energy densities,which are superior to most reported MOF-based supercapacitors.This work reveals the potential application of redox-active c-MOFs in supercapacitor-related fields.Secondly,a nitrogen-rich and electron-deficient tricycloquinazoline（TQ）based multitopic catechol ligand was employed to coordinate with transition metal ions(Cu²⁺and Ni²⁺),which therefore,formed 2D graphene-like porous sheets:M3（HHTQ）2（M=Cu,Ni;HHTQ=2,3,7,8,12,13-Hexahydroxytricycloquinazoline）.MO4 moieties in M3（HHTQ）2 can be regarded as sigle-atom catalystic sites for carbon dioxide reduction reaction（CO2RR）where Cu or Ni centers are uniformly distributed in the hexagonal lattices.M3（HHTQ）2 can be used as electrocatalysts to reduce CO2 to CH3OH with high selectivity.Specially,Cu3（HHTQ）2 exhibits high effiency and good durability,while isostructural Ni3（HHTQ）2 and the reported Cu3（HHTP）2 only show poor performance.Systematacially electrochemical tests and theoretical calculations further indicate the reasons for the large performance variation between Cu3（HHTQ）2,Ni3（HHTQ）2 and Cu3（HHTP）2,as well as speculate the possible reaction mechanisms.The current work achieves the precise regulation of CO2RR performance from rational ligand design and judicious metal center selection,and provides new possibilities to develop novel 2D c-MOF-based electrocatalysts toward efficient CO2RR.Thirdly,a quinone-containing multidentate catechol ligand,2,3,6,7-tetra（3,4-dihydroxyphenyl）anthracene 9,10-dione（8OH-TPAQ）,was designed and synthesized,and further coordinated with Cu²⁺to construct a new 2D c-MOF,namely Cu-TPAQ.Cu-TPAQ showcases not only intrinsic porosity,decent electrical conductivity and good stability,but also highly reversible redox behavior due to the introduction of quinone moieties.Cu-TPAQ was employed as cathode for zinc ion batteries（ZIBs）,which showcases high specific capacity and excellent electrocahemical stability.This work has successfully integrated the quinone moieties with high redox characteristics into 2D c-MOFs and used as high-efficiency ZIBs cathode,which not only enhances the specific capacity but also stabilizes the electrochemical performance of 2D c-MOF-based electrodes during redox process.Finally,three twisted hexabenzocoronene-based multidentate catechol ligands were designed and synthesized,namely 6OH-HBC,8OH-HBC and 12OH-HBC.These three HBC ligands were reacted with copper nitrate trihydrate via solvothermal method to prepare Cu-HBC-6OH,Cu-HBC-8OH and Cu-HBC-12OH,respectively.Because of the different numbers of hydroxyl groups and different ligand symmetries,the HBC MOFs showcase distinct differences in electrical conductivities,pore structures,and density of redox-active sites.In order to clearly understand the structure-property relationship,the three HBC MOFs were utilized as cathodes for lithium-ion batteries.Thanks to the shorter electron transport path,higher conductivity and more redox sites,Cu-HBC-12OH electrode showcases higher specific capacity and better rate ability.In this work,the regulation and control of structure,electrical conductivity and lithium ion storage capacity of 2D c-MOFs were realized through reasonable molecular design.