Controllable Growth Of MOFs Thin Films And Applications In Electrochemical And Fluorescence Sensing

Metal-organic framework（MOFs）thin films have important application prospects in the fields of sensors,electronic devices,and membrane separations.In this paper,a bottom-up strategy is adopted to grow ferrocene（Fc）functionalized on Au electrodes of pyridine or purine-functionalized self-assembled monolayers（SAMs）via layer-by-layer（LBL）.The MOFs thin films are prepared,and their electrochemical properties and charge transport mechanism are studied;Cu-Pyrazolate MOFs are synthesized at the oil-water interface and transferred to the surface of conductive glass（ITO）by the interfacial synthesis method;M（Ⅱ）-BTC（M=Ni,Co,Mg）and lanthanide Ln-MOFs（Ln=La,Ce,Pr,Sm,Eu,Gd,Tb,Ho and Er）and thin films,and study the effect of Tb-MOF on the containing Fluorescence detection of amino small molecules.The main research content of this paper consists of the following three parts:（1）Layer-by-layer self-assembly growth and electrochemical performance of ferrocene-functionalized MOFs thin filmsH₂bpdc-Fc organic ligand was synthesized by grafting ferrocene（Fc）on the side chain of biphenyl dicarboxylic acid（H₂bpdc）using the ligand grafting strategy.Redox-active（redox）MOFs films（SURMOFs）,named[Cu₂（bpdc-Fc）₂dabco]SURMOFs,are grown on the functionalized surface of 6-mercaptopurine self-assembled monolayers（SAMs）.High-density tetragonal prism-like[Cu₂（bpdc-Fc）₂dabco]nanocrystals are obtained on the surface of 6-mercaptopurine SAM,and cyclic voltammetry（CVs）tests showed that at E_pa=0.86 V and E_pc=0.43 V(relative to Ag/Ag Cl,E_1/2=0.65 V),a pair of redox peaks are observed.In contrast,[Cu₂（bpdc-Fc）₂dabco]SURMOFs grow on the surface of4-mercaptopyridine SAM have insignificant redox peaks due to factors such as low crystal density and many defects.Combined with the potential step chrono-coulomb method,the charge transport mechanism of[Cu₂（bpdc-Fc）₂dabco]SURMOFs is proposed to be a[Fc⁺/Fc]redox hopping mechanism within the MOFs framework,accompanied by the diffusion of electrolyte into the framework to achieve charge balance.The apparent diffusion coefficients are calculated using the Randles-Sevcik equation and the Anson equation,which are 2.96×10^-11 cm~2/s and3.2×10^-11 cm~2/s,respectively.（2）Liquid-liquid interface method to synthesize Cu-MOFs thin filmsThe pyrazolyl-functionalized organiclig and N,N’-bis（3,5-dimethyl-1H-pyrazole）is synthesized by the interfacial synthesis method using the organic solvent dichloromethane or n-butanol and an aqueous solution to form an oil-water interface.1,4,5,8-Naphthalenetetracarboxyldiimide（PZ-NDI）and 1,3,5-tris（4-4-pyrazolylphenyl）benzene（H₃BTPP）are dissolved in the organic phase,The copper acetate is dissolved in the water phase,and after standing,a blue Cu-MOFs film was synthesized at the oil-water interface.The Cu-MOFs at the n-butanol/water interface are regular hexagonal microplates,while the Cu-MOFs obtained at the methylene chloride/water interface are micron regular hexagonal crystals.（3）Synthesis of M（Ⅱ）-BTC（M=Ni,Co,Mg）and lanthanide Ln-MOFs（Ln=La,Ce,Pr,Sm,Eu,Gd,Tb,Ho and Er）using ZnO as sacrificial agent)and thin film and fluorescence sensing applicationsRapid synthesis of M（Ⅱ）-BTC（M=Ni,Co,Mg）and lanthanide Ln-MOFs（Ln=La,Ce,Pr,Sm,Eu,Gd,Tb）at room temperature using ZnO as precursor,Ho and Er)and thin films,the crystal structures and morphologies of the above MOFs are investigated by X-ray Powder Diffraction（XRD）and Scanning Electron Microscopy（SEM）.The results show that although Co-BTC and Ni-BTC have different morphologies,which are microrods and hexagonal columns,respectively,both have similar crystal structures,the crystal structures of Mg-BTC nanorods are different from those reported.Except for Eu-BTC which is a nanoparticle,the other Ln-BTCs have nanorod morphology,but La,Ce and Pr-BTC have the same structure,while Sm,Gd and Eu-BTC have related crystal structures.The steady-state fluorescence spectra show that Tb-BTC and Eu-BTC exhibited corresponding characteristic Tb and Eu fluorescence emission peaks at 544 nm and 615 nm,respectively,when excited at 268 nm.Using the characteristic fluorescence emission peaks of Tb-BTC,the fluorescence quenching detection of aniline,2-aminodiphenylamine and ofloxacin is studied.It has a good linear relationship in the concentration range of 0～140μM.On the basis of the synthesis of bulk Ln-MOFs,Tb-BTC and Eu-BTC MOFs films are synthesized using ZnO films as precursors,and their morphology and luminescence properties are studied.