| Volatile Organic Compounds（VOCs）are very important sources of air pollution and seriously threaten human health and the ecological environment.Photocatalytic oxidation technology is considered to be one of the most promising VOCs treatment technology,but due to the small specific surface area and high photocatalytic generated carrier recombination characteristics of commonly used semiconductor catalysts,their visible light degradation efficiency of VOCs is low and catalyst deactivation often occurs,which greatly restricted the practical application of photocatalytic oxidation technology in the purification of VOCs.As a porous material with large specific surface area and semiconductor-like properties,metal organic frameworks（MOFs）materials have gradually attracted researchers’attention in the fields of VOCs adsorption and photocatalysis.Especially for the two-dimensional MOF nanosheets developed in recent years,its ultra-thin structure is expected to expose more catalytically active sites,accelerate the adsorption and mass transfer of reactive molecules,and improve the photogenerated electron transport capability.In this thesis,foam nickel is used as the substrate and sacrificial template of MOFs nanosheets.Ni-MOF nanosheet arrays were found to be uniformly grown on the surface of foam nickel prepared in one step by solvothermal method and electrochemical deposition method,respectively.The assembly problems in practical industrial applications were successfully resolved.Three typical VOCs of ethyl acetate,n-butanol and toluene discharged from the paint spraying industry as the research object,were selected for the adsorption and photocatalytic performance of the prepared catalyst,and the catalyst prepared mechanism and efficient degradation mechanism of typical VOCs were also systematically explored.The main research contents of this paper are shown as follows:1)A one-step solvothermal method was developed to grow Ni-MOF nanosheet arrays（Ni-MOF/NF）in situ on the surface of nickel foam to achieve uniform and vertical growth of Ni-MOF nanosheets on the surface of nickel foam.Moreover,the distance between adjacent nanoplates is about several tens of nanometers,which effectively suppresses the agglomeration and lateral stacking between the nanoplates,and solves the problem that MOFs catalysts are difficult to assemble and apply in practical applications.The catalyst characterization results show that the large-pore nickel foam and uniformly distributed ultra-thin Ni-MOF nanosheets in the Ni-MOF/NF composite are conducive to light penetration and exposure of the light absorption center,and Ni-MOF/NF exhibits higher light absorption strength than powdered Ni-MOF and nickel foam.Under visible light irradiation,Ni-MOF/NF can rapidly degrade ethyl acetate,n-butanol and toluene,while powdered Ni-MOF and pure nickel foam show almost no photocatalytic activity.2)The mechanism research shows that due to the lack of fast electron transfer channels,powdered Ni-MOF has an interface charge transfer impedance as high as 791times that of Ni-MOF/NF,and the steady-state photocurrent intensity is reduced by about seven orders of magnitude compared to Ni-MOF/NF,so that under the visible light irradiation,the powdered Ni-MOF hardly produced·O2-and·OH radicals,and showed almost no photocatalytic activity to degrade VOCs.In the Ni-MOF/NF composite material,the porous nickel foam support in Ni-MOF/NF composites and the non-stacked Ni-MOF nanosheets array synergistically improve the mass transfer and diffusion of substrate molecules,light absorption and separation of photo-generated carriers.This results in a large amount of strongly oxidizing·OH,·O2-and other free radicals on the catalyst surface,which can be quickly consumed by the reaction substrate molecules,reducing the accumulation of intermediate products on the catalyst surface.Therefore,the photocatalytic activity and anti-deactivation capability of the catalyst are improved.Furthermore,PTR-To F-MS was used to online monitor the distribution of ethyl acetate degradation products at different flow rates to clarify the possible reaction pathway of photocatalytic degradation of ethyl acetate on Ni-MOF/NF catalyst.The results show that the degradation products mainly include formaldehyde,acetaldehyde,formic acid,ethanol,acetic acid and acetone,and speculate that the photocatalytic reaction may involve three reaction paths.3)Develop an in-situ constant voltage electrochemical deposition method,and realize the controllable preparation of Ni-MOF film on the nickel foam surface by regulating the applied voltage and reaction temperature.The condition optimization results show that the thickness of the Ni-MOF film on the nickel foam surface is thicker as the reaction temperature increases.The typical VOCs and ethyl acetate emitted by the paint spraying industry were selected as model compounds.The photocatalytic performance of the Ni-MOF film material synthesized by electrochemical deposition method was systematically investigated.The results show that the Ni-MOF film material prepared at70°C exhibits the best photocatalytic degradation activity,and the removal rate and mineralization rate of ethyl acetate are as high as 86.8%and 64.6%,respectively. |
