The Preparation Of Ni- Or Zn-MoFs And Catalysts For The Conversation Of CO₂

The problem of carbon dioxide?CO₂?excessive emission is more and more serious now.Therefore,there is an urgent need to develop multiple methods to capture and convert CO₂ into useful chemical products.The most prospect and widely studied way is synthesis of cycle carbonate with 100% atom economy characteristics of CO₂ and epoxide.Due to the inactivity of CO₂ and the harsh condition of reactions,we explored two kinds of efficient porous catalysts with solvothermal method to catalysis the reaction epoxides and CO₂.The first of catalysts is Ni-MOF which was synthesized by nickel nitrate as metal ion source and imidazole carboxylic acid as organic ligands.The structure and composition were characterized by IR,EA,XRD,XPS,TGA,N2adsorption/desorption the adsorption of CO₂.And then the catalytic activity of Ni-MOF on the coupling reaction of CO₂ and propylene oxide was studied,including reaction temperature,reaction time,catalyst and dosage on the catalytic activity,TBAB was the most suitable catalyst,and the optimized reaction conditions were confirmed as 120 oC,2 MPa,6 h,The yield and of propylene carbonate reached 97%.In addition,due to Ni-MOF had nitrogen atoms and microporous structure,the adsorption of CO₂ on this catalyst is prominent?59.5 cm3/g?.The Zn-MOF catalyst had been successfully synthesized through solvothermal method with melamine?richer in nitrogen?as one of the ligands and zinc nitrate?more active of epoxides?as metal ion source,and then,the characterization of Zn-MOF was characterized by X-ray crystallography,XRD,XPS,TGA,and N2 and CO₂ adsorption.Moreover,the influences of the catalytic activity were investigated,including reaction temperature,reaction time,co-catalyst dosage,CO₂ pressure,and the reaction parameters were optimized.Due to the Zn-MOF catalyst had the large number of nitrogen atoms and the pore structure,the properties of Zn-MOF to adsorption of CO₂ was extremely outstanding,and the adsorption capacity reached 108.9 cm3/g,while the large surface area and the existence of free amino groups,carboxyl groups also promoted the catalytic activity.The yield and selectivity of propylene carbonate reached98% and 99% at the optimized reaction conditions?80 oC,1 MPa,3 h?,and catalyticconversion could react at room temperature efficiently,The yield and of propylene carbonate reached above 95%.In addition,the Zn-MOF catalyst was efficiently versatile to the coupling of CO₂ with other epoxides and the conversions could also reach more than 90%,such as epoxy chloropropane,epoxy butane,styrene oxide,etc.Additionally,the catalyst possessed excellent chemical and thermal stability,and good recycling performance,after repeated uses for three times,there was no significant loss of catalytic activity.Finally,based on the experimental results and the characterizations of the catalyst,the catalytic mechanism was proposed and discussed.