Research On Properties Of Two-dimensional MOFs Nanosheets And Their Derivative Materials

In recent years,MOFs has become one of the fastest-growing research directions in the field of chemistry and materials.But the work mainly focuses on large MOFs crystals,0-dimensional MOFs nanoparticles and 1-dimensional MOFs nanowires.There was little research on two-dimensional MOFs nanocrystals.Compared with three-dimensional traditional MOFs,two-dimensional MOFs nanosheets not only has the advantages of low density,large internal specific surface area,abundant pore channels,and good stability of the MOFs material,but also the unique laminar structure,which makes it have high external specific surface area,thin thickness,and exposed active sites.So the two-dimensional MOFs nanosheet has good applications in separation,catalysis,and film fields.The traditional MOFs have poor conductivity,which limited its application in the field of photocatalysis and electrocatalysis.The design of two-dimensional MOFs nanosheets and the preparation of derivatives from MOFs are two effective measures to make up for the poor conductivity of MOFs.Because zeolite imidazolyl skeleton（ZIFs）MOFs has good chemical stability and excellent adsorption performance,the research in this paper is based on ZIFs MOFs.In this paper,the two-dimensional MOF sheets with layered structure were prepared by surfactant assisted synthesis method.During the formation of ZIF MOFs,surfactants were adsorbed on the surface of nano MOFs,which can prevent the vertical growth of MOF in three dimensions and facilitate the formation of layered structure.Furthermore,the derivatives based on two-dimensional MOF nanosheets were obtained via hydrothermal treatment and their catalytic properties were studied.The main research contents of this thesis are as follows:（1）Preparation and properties of the two-dimensional MOFs nanosheetsTo prepare ZIF-8 MOF nanosheet and Zn-Co bimetallic MOF nanosheet,the surfactants were added to prevent the vertical growth of MOF in three dimensions.The structure and morphology of the materials were characterized by FT-IR,XRD,XPS,SEM,TGA and BET,and their photocatalytic and electrocatalytic properties were tested,respectively.（2）Preparation and photocatalytic performance of C/N@Zn O/Ag derived from ZIF-8MOF nanosheetFirstly,the two-dimensional ZIF-8 sheet is hydrothermally treated.The ZIF-8 sheet undergoes structural transformation and formed the C、N-coated Zn O nanorods.In order to improve the photocatalytic performance of Zn O nanorods,Ag nanoparticles were loaded and C/N@Zn O/Ag composites were prepared.The structure and morphology of the material were characterized by FT-IR,XRD,XPS,SEM and TEM.The photocatalytic activity of the catalyst was studied by the Uv-visible diffuse reflectance spectra,fluorescence spectra,transient/steady fluorescence spectra and electrochemical impedance spectra.The C/N@Zn O/Ag composites showed the high photocatalytic efficiency for degradation of MB.The kinetic degradation rate constant of the C/N@Zn O/Ag composites is 0.0224 min^-1,which was 7.5 times that of the commercially available P25(0.0032 min^-1).After recycling,the photocatalytic performance of the composites was almost unchanged,indicating its good stability.（3）Preparation and catalytic performance of C/N@Zn Co₂O₄nanorod derived from bimetallic Zn-Co MOF nanosheetThe C/N@Zn Co₂O₄nanorods were obtained from the bimetal Zn-Co MOF nanosheet by adjusting the polarity of dispersant in the hydrothermal process.FT-IR,XRD,XPS,SEM,TGA,BET and other test were used to characterize the structure and morphology of the material.The results showed that the C/N@Zn Co₂O₄nanorods had the high specific surface area,reasonable pore size distribution.Finally,the OER catalytic performance of catalysts was evaluated by linear cyclic voltammetry and electrochemical impedance spectroscopy.