Fabrication Of MOFs Incorporated With Metal Complexes And Their Electrocatalytic And Analytical Applications

Metal-organic frameworks（MOFs）have been widely used in various catalytic fields,including electrocatalytic oxygen evolution reaction（OER）and electrocatalytic oxidation of small molecules,due to their exceptional properties,such as high porosity,large specific surface area,and tunable structure.Nevertheless,the catalytic performance of MOFs is hampered by inherent limitations such as poor conductivity,low mass transfer efficiency,and poor stability.Therefore,numerous strategies have been developed to enhance the catalytic performance of MOF-based catalysts.Numerous studies have indicated that introducing monocarboxylate ligands to synthesize defective MOFs can effectively improve the catalytic performance of MOFs.However,few studies have focused on the role of ligands in improving the overall catalytic performance of MOFs.Therefore,this study taked Ni-based MOFs as the main research objects.The influence of the electron donating and withdrawing properties of doped monocarboxylate ligands,and ferrocene derivatives as doped ligands on the catalytic performance of 3D MOFs were investigated.On the other hand,many studies have shown that MOFs with high porosity are ideal carriers for encapsulating complex.The effective control of doping can be realized through encapsulation,and the molecular structure formed is more clear.Therefore,a 2D Ni-based MOF with higher porosity was used to encapsulate ferrocene derivatives to form a well-defined composite material.The primary contents of this study are as follows:（1）A one-step solvothermal method was employed to dope monocarboxylate ligands,which possess electron-donating or electron-withdrawing properties into Ni-BDC,and the OER properties of the synthesized catalysts were investigated.The experimental results showed that the defects formed by doping monocarboxylate ligands had limited effect on the OER performance of Ni-BDC.Moreover,there was no significant difference in the influence of electron-donating and electron-withdrawing properties of doped ligands on the OER performance of Ni-BDC.However,the OER performance of Ni-BDC was significantly improved when the metal complexs（ferrocenecarboxylic acid）with electron-donating properties was doped.We speculated that this might be related to the properties of ferrocene derivatives themselves.To confirm this hypothesis,Ni-BDC and other metal-based MOFs doped with 1,1’-ferrocenedicarboxylic acid（1,1’-Fc）were prepared.The results of electrochemical performance tests and characterization analysis of the catalysts indicated that the active sites of the catalysts were not located on the ferrocene ligands.The significant performance improvement was mainly due to the strong synergistic effect between the delocalized-electron-rich ferrocene derivatives and MOFs.Meanwhile,density functional theory（DFT）calculation further confirmed the above conclusion.Among the prepared catalysts,1,1’-Fc-Ni-BDC showed good OER performance,the overpotential was 387 m V when the current density was 10 m A cm^-2,and had good electrochemical stability.In addition,1,1’-Fc-Ni-BDC also showed good performance of electrocatalytic oxidation of glucose:high sensitivity(2453.0μA m M^-1 cm^-2),low detection limit（11.0μM,S/N=3）,and wide linear range（0.01～1.5 m M）.（2）2D condutive Ni-HHTP framework was synthesized through the hydrothermal method.It was then immersed in the solution of ferrocene derivatives and stirred,and the ferrocene derivatives were absorbed into the cavity of Ni-HHTP by the electrostatic attraction to form Fc-Ni-HHTP.Compared with Ni-HHTP,Fc-Ni-HHTP showed superior OER performance,with an overpotential of 482 m V at the current density of 10 m A cm^-2,and showed excellent electrochemical stability.Moreover,Fc-Ni-HHTP demonstrated good performance of electrocatalytic oxidation of glucose:high sensitivity(2773.2μA m M^-1 cm^-2),low detection limit（64.6μM,S/N=3）,and wide linear range（0.03～1.0 m M）.The results showed that the superior electrocatalytic performance of Fc-Ni-HHTP can be attributed to the synergistic effect between the ferrocene derivatives and Ni-HHTP,which regulated the electronic structure of the active sites,thereby enhancing the OER performance of the catalysts.Density functional theory calculations also confirmed that the molecular structure of the composite was clear,and the significant role of the encapsulated ferrocene derivative in regulating the OER activity of the catalysts.