Study On The Construction Of New Polymer Photocatalyst And The Catalytic Degradation Performance Of No_x

With the rapid development of modern industry,people’s living standards are continuously improved.However,the frequent use of fossil fuels in industrial production has spawned a large number of polluting gases and caused serious damage to the atmospheric environment.With the rapid economic development and the continuous improvement of people’s living standards,the burning of a large amount of fossil fuels,including automobile exhaust,power plant exhaust and factory exhaust,has caused serious gas pollution problems to the environment.NO_X is a major pollutant gas produced by the burning of fossil fuels.NO_X is one of the main pollutants in the pollutant gas emitted.It not only causes environmental pollution such as acid rain,haze and photochemical smog,but also causes great harm to human health,such as cancer and cardiovascular diseases.but also causes great harm to human health,and can induce cancer and cardiovascular diseases.Therefore,it is necessary to effectively control a large amount of pollutant gas emissions,and the degradation of pollutant emission reduction is the most important method currently adopted.Photocatalysts can absorb light to redox reactants,which is a green and healthy means for degrading pollutants.However,traditional semiconductor catalysts are mainly metal oxides such as Ti O₂,Zn O,Bi OCl,and bismuth salts,which are not only difficult to absorb visible light,but also have low photo-generated carrier separation efficiency,resulting in low photocatalytic degradation activity.Compared with traditional semiconductor materials,metal organic framework（MOFs）materials have a larger specific surface area and porous structure,which is very conducive to gas adsorption.However,the defects of large band gap and the large separation resistance of photogenerated carriers greatly limit the application of this type of material in the field of photocatalysis.This paper systematically studied how to reduce the visible light of UIO-66（Hf）materials through ligand functionalization.Absorption capacity,and developed a new synthesis method,controllable introduction of ligand defects in UIO-66（Hf）,which greatly improves the photogenerated carrier separation ability of UIO-66（Hf）.By adjusting the electronic structure of UIO-66（Hf）,the photocatalytic activity of the material is fundamentally improved.The research content of this paper is mainly divided into the following parts:1.Ligand functionalization unlocks the photocatalytic potential of MOFsThrough functionalization of the ligand of UIO-66（Hf）material-terephthalic acid,the effect of different types and different numbers of groups on the degradation of NO_Xperformance of UIO-66（Hf）material under visible light was studied.performance of UIO-66（Hf）material under visible light was studied.The study found that the ligand is mainly responsible for the light absorption and electronic excitation of UIO-66（Hf）material.And found that the introduction of electron-withdrawing groups in the ligand can reduce the energy required for electronic excitation by increasing the form of LUMO;the introduction of electron-donating groups can reduce the energy required for electronic excitation by introducing non-bonded orbitals between energy levels Energy;and the introduction of special groups,such as-SO3H,-COOH,etc.,due to the simultaneous presence of electron-withdrawing parts S,C and electron-donating parts-OH in their groups can not effectively reduce the energy required for electronic excitation.It has also been found that whether modifying two electron-donating groups or electron-withdrawing groups in the ligand can effectively increase the absorption capacity of UIO-66（Hf）for long-wavelength light,it can effectively reduce the energy required for excitation.However,after introducing four electron withdrawing groups,the energy of theπelectron cloud decreases due to the symmetrical attraction of the electron withdrawing group to theπelectron cloud,which makes it difficult for electrons to transition,which increases the energy required for electron excitation.The synthetically prepared Br₂-UIO-66（Hf）under visible light（λ≥420 nm）has 80%degradation efficiency for NO_X in the mobile phase,and can effectively inhibit the formation of NO₂.2.High-pressure microwave method---breaking the barrier of MOFs photocatalysisA high-pressure microwave synthesis method was developed for the preparation of high-performance UIO-66（Hf）,which can controllable the introduction of ligand defects in UIO-66（Hf）by controlling the gas pressure and the amount of formic acid during the synthesis process.The introduction of ligand defects can reduce the energy ofΔE_LMCT,reduce the separation resistance of photogenerated carriers,thereby increase the separation efficiency of photogenerated carriers,and improve the efficiency of light utilization.Through the combination of theory and experiment,the formation mechanism of defects in the process of high-voltage microwave synthesis is proposed.Among them,the microwave greatly accelerates the formation of hafnium tetrachloride in the precursor liquid to form hafnium oxygen clusters,so that the hafnium oxygen clusters in UIO-66（Hf）and the organic ligands form unsaturated coordination;Applying high pressure,the UIO-66（Hf）octahedral cage can be squeezed to deform it,resulting in a smaller coordination space where the ligand is not connected,so that it cannot form a coordination with the ligand and retain the material.defect.Through the controllable introduction of ligand defects,the density of states of UIO-66（Hf）can be changed to reduce the energy ofΔE_LMCT,fundamentally change its electronic mechanism,and increase the separation ability of photo-generated carriers.For UIO-66 materials,the catalyst activity is generally improved by supporting precious metals and composite catalysts.The use of high-pressure microwave methods to improve catalyst activity has the advantages of simple operation,low cost,and significant catalytic activity improvement effect,which is of great significance for the development of MOFs with high photocatalytic performance.