Electron-Donating Groups Regulate The Organic Pollutants Oxidative Degradation By Photocatalysts:Mechanism Research And Material Functions Enhancement

Residual organic pollutants in water are a challenge in current water treatment and water quality safety due to their low concentration and difficulty of microbial degradation.The development of new,safe,efficient and energy-saving water treatment technologies can effectively guarantee the safety of water quality.Photocatalytic oxidation technology can directly use solar energy to drive a series of chemical reactions.It has the advantages of low energy consumption,mild reaction conditions and no secondary pollution.Which is an effective method to solve residual organic pollutions in water.The key to achieve this process is to find and design efficient photocatalysts.The current photocatalytic materials are mainly composed of inorganic semiconductors,which are limited in their practical application due to their low efficiency of absorption and utilization of sunlight and difficulty in structural modification.This thesis develops a highly efficient,inexpensive,and stable photocatalyst,which are controlled and constructed by electron-donating groups.They are verified photocatalytic performanceand by catalytic oxidation of phenanthrene in polycyclic aromatic hydrocarbons,methylene blue in dye pollutants,and coking wastewater with high toxicity in industrial wastewater.The systematic study of the removal efficiency,kinetics and degradation mechanism of these typical target pollutants by different electron-donating groups modified and constructed photocatalysts.The results of UV-Visible diffuse reflectance spectroscopy（UV-Vis DRS）and the photocatalytic degradation of phenanthrene in water both proved that the stronger the electron-donating groups in MIL-101（Fe）-X and UIO-66-X（X=-OH,-NH₂,-COOH,-NO₂,and-H）,the better the photocatalytic efficiency,and the catalytic efficiency followed the order of-OH>-NH₂>-COOH>-NO₂>-H.This order was due to the electronegativity regulation of the MIL-101（Fe）-X and UIO-66-X by ligand-to-metal charge transfer（LMCT）.According to the regulation of electron-donating groups,the[Cu（L）₂·（CN）]_n（L=4-（3H）-quinazolinone）and{[Cu^Ⅱ（H₂O）₄][Cu₄^Ⅰ（CN）₆]}_n,which are instructed and synthesized in situ by-CN.The in-situ synthesis mechanism of[Cu（L）₂·（CN）]_n indicates hollow metal ion sites in the complexes play a major role in the catalytic C-C bond cleavage.The[Cu（L）₂·（CN）]_n photocatalyst has visible light response,which cleaves the amide bond in the methylene blue molecular structure during photocatalytic degradation of the organic dye methylene blue molecule,and then further cleaved into small molecular acid,CO₂ and H₂O.This method of using low-toxicity acetonitrile as a raw material to introduce-CN by metal ion-catalyzed C-C cleavage provides a new methodology for in situ synthesis-CN photocatalyst.{[Cu^Ⅱ（H₂O）₄][Cu₄^Ⅰ（CN）₆]}_n is a coordination polymer composed of inorganic ions and can be called as inorganic coordination polymer（ICP）.It has over 50%light absorption in the UV-Vis range of 200-720 nm and can utilize visible light to efficiently photocatalyze the organic dye methylene blue.When it was successfully stripped into amorphous quantum sheets（QS）,the rate of photocatalytic degradation of methylene blue was greatly improved to2.50·L^-1·minute^-（1）due to the utilization of more metal sites.Moreover,even if a large amount of inorganic ions are present,this ICPQS still can effectively photocatalyze degradation of methylene blue molecules.In addition,the experimental results also show that this ICPQS can efficiently degrade the phenolic pollutants in the actual industrial coking wastewater and the residual aniline and quinolone organic pollutants in biochemically treated coking wastewater.This kind of quantum sheets that based on mixed valence paves the way for developing the next-generation monolayer two-dimensional material photocatalysts for capturing a broad range of the solar spectrum for environmental decontamination.In this thesis,through the systematic study of the effect of electron-donating groups on photocatalysts,the obtained electron-donating group regulation law not only provides a theoretical basis for designing and synthesizing new and high-efficiency photocatalysts in the future,but also provides a technical methodology for broadening photocatalysts in practical wastewater applications.