Preparation Of Carbon Cloth Loaded NH₂-UiO-66 Film And Their Photocatalytic Degradation Mechanism For Ethyl Acetate

With the development of industry,volatile organic compounds（VOCs）have become one of the most important sources of air pollution in China.Photocatalytic oxidation technology has the advantages of mild reaction conditions and strong oxidation ability,and thus is considered to be one of the most promising VOCs treatment technologies.However,commonly used semiconductor photocatalysts often face the shortcomings of fast photogenerated carrier recombination and small specific surface area,resulting in unsatisfactory photocatalytic degradation of VOCs.As a new class of porous photocatalysts,metal-organic frameworks（MOFs）have attracted much attention due to their large specific surface area,high porosity,tunable photoredox activity and light absorption properties.However,how to effectively improve the separation of photogenerated electrons and holes is still a challenging topic in this field.Considering the excellent electron transport ability,high chemical stability and thermal stability of carbon fiber cloth,loading MOF on the surface of carbon fiber cloth is expected to improve the photogenerated electron transport rate,thereby improving the separation of photogenerated electrons and holes in MOF.Therefore,in this thesis,the NH₂-Ui O-66 thin film（NH₂-Ui O-66@CC）supported on the surface of carbon fiber cloth was directly prepared by one-step electrochemical deposition using carbon cloth as the substrate.Ethyl acetate emitted from industrial spraying industry was chosen as a model VOC to evaluate the photocatalytic oxidation activities of the NH₂-Ui O-66@CC composites prepared by different deposition times.Furthermore,the separation efficiency of photogenerated electrons and holes,the transfer mechanism of photogenerated electrons as well as the surface information such as the generated main radicals in NH₂-Ui O-66@CC during the photocatalytic process were obtained by using steady/transient state photoluminescence spectroscopy,in-situ XPS,photoelectrochemical measurements and electron paramagnetic resonance spectrometer.Finally,a plausible mechanism for photocatalytic degradation of ethyl acetate by NH₂-Ui O-66@CC was proposed.The main research contents of this thesis are as follows:（1）The NH₂-UiO-66 precursors containing zirconium tetrachloride and 2-aminoterephthalic acid were dissolved in DMF and acted as the electrolyte.A standard three-electrode system was used,in which clean carbon cloth directly served as the negative electrode.A constant voltage was applied at the carbon cloth working electrode for the required time to induce the growth of NH₂-Ui O-66 on the surface of the carbon fiber cloth.The characterization results showed that NH₂-Ui O-66 films can successfully grow on the surface of carbon cloth with controlled thicknesses,and NH₂-Ui O-66 could form good interfacial contact with carbon cloth.（2）The photocatalytic degradation performance of ethyl acetate by NH₂-Ui O-66@CC,bare carbon fiber cloth,NH₂-Ui O-66 powder,and NH₂-Ui O-66/CC（smear method）was investigated.Carbon cloth did not show catalytic activity,and the mineralization rates of NH₂-Ui O-66 powder and NH₂-Ui O-66/CC for ethyl acetate were 6%and 15%,respectively.Remarkably,NH₂-Ui O-66@CC-30 exhibited 30%mineralization rate to ethyl acetate,which was 6 times and 2 times higher than that of NH₂-Ui O-66 powder and NH₂-Ui O-66/CC,respectively.（3）By means of photoelectrochemical measurements,electron paramagnetic resonance spectroscopy（EPR）,steady/transient state fluorescence spectroscopy and in situ X-ray electron spectroscopy,the transfer pathways of photogenerated electrons,the separation efficiency of photogenerated electrons and holes as well as the surface information such as the formed main radicals in NH₂-Ui O-66@CC during the photocatalytic reaction were investigated in detail.The results showed that NH₂-Ui O-66@CC exhibits the smallest electron transfer resistance and the strongest photogenerated electron-hole separation efficiency under UV-vis illumination.Such features made NH₂-Ui O-66@CC produce the most·O₂^-,·OH and other strong oxidizing free radicals among the investigated photocatalysts,which could attack and decompose ethyl acetate.Finally,NH₂-Ui O-66@CC displayed significantly improved photocatalytic degradation activity of ethyl acetate compared to carbon cloth,NH₂-UiO-66powder and NH₂-UiO-66/CC.