Controlled Preparation And Catalytic Performance Of MOFs Derived Oxides Supported Noble Metal Catalysts

With the development of society,the problem of air pollution has become increasingly prominent,and the treatment of pollutants is important.Volatile organic pollutants（VOCs）can be called the culprit of air pollution phenomena such as smog.Catalytic oxidation is widely recognized as an effective means of eliminating VOCs and has excellent development prospects.The research and development of catalysts is the key to catalytic oxidation methods.Precious metal catalysts have excellent low-temperature oxidation activity,but easy to sinter.Therefore,the strategy of supporting precious metal nanoparticles with porous materials is often adopted,which conducive to the dispersion of precious metal particles,improve thermal stability,and thereby extend the life of the catalyst.And the specific support often shows the interaction with the active center of the precious metal,which further improves the catalyst performance.Metal-organic framework materials（MOFs）is a kind of new porous nano-materials,which has the characteristics of controlled pore size,structure tailor ability,and surface functionalization.It has broad application prospects in the fields of gas adsorption,hydrogen storage and catalysis.At the same time,compared with traditional molecular sieves,MOFs can directly introduce metal sites.However,MOFs generally has poor stability at high temperatures,making it difficult to apply to the catalytic oxidation of VOCs.Therefore,this dissertation respectively heat-treated MOFs under different atmospheres,two kinds of catalysts were designed and prepared:Ce-BTC derived CeO₂supported Pd NPs and ZIF-67 derived Co₃O₄ supported Au NPs.Various techniques were used to characterize the physical and chemical properties of those two series of catalysts,and the catalytic activity was evaluated by benzene or carbon monoxide oxidation reactions,the structure-activity relationship was established.The main research results of this dissertation are as follows:（1）The one-pot method is used to combine the process of reducing Pd precursors into nanoparticles and the Ce-BTC self-assembly process.By controlling the reaction temperature,Ce-BTC loaded Pd is prepared,and then calcined at high temperature in different atmospheres.New catalysts（in-situ xPd-CeO₂,x=1wt%）was prepared.Through the characterization of catalysts,it was found that it has an irregular stick-like morphology,and Pd nanoparticles are highly dispersed therein.Compared with the catalysts prepared by two-step method（y Pd/CeO₂,y=1wt%）and bulk catalysts（0.98Pd/bulk CeO₂）,this series of catalysts show better catalytic activity for the oxidation reaction of carbon monoxide.This is related to the high dispersibility exhibited by the in-situ reduction of Pd in one-pot method and the interaction between the support and the active site.The samples in a protective atmosphere showed a stronger ability to adsorb oxygen species.（2）ZIF-67 modified with different concentrations hexadecyltrimethylammonium bromide（CTAB）was used as a precursor,which calcined in air and nitrogen at different temperatures to prepare Co₃O₄ with a specific morphology,and their supported Au nanocatalysts（z Au/Co₃O₄,z=0.05wt%）.Compared with bulk catalyst（0.04Au/bulk Co₃O₄）,z Au/Co₃O₄ catalyst showed better catalytic performance for toluene oxidation reaction.The porous structure of the support and the reduction of the grain size are the key influencing factors.