Design And Catalytic Application Of Hollow UiO-66 Nanospheres

Hollow metal-organic frameworks(MOFs)possess various advantages,such as enchanced gas-adsorption properties,large specific surface area,high porosity,fast mass transfer rate,etc.In addition to the advantages of hollow nanostructures,hollow MOFs aslo possess some inherent properties from the MOFs.For example,the ability of electron-donating/withdrawing to functional groups on the organic ligands in MOFs,can adjust the electron density of coordination groups with metal ions and the morphology of materials themselves.In addition,the ligands in MOFs are modifiable,and new specific functional groups can be introduced into the framework through functionalization,which will give MOFs materials the required physical and chemical properties and achieve the purpose of improving their catalytic activity in specific reactions.Hence,we used hollow MOFs as the carrier for Pt nanoparticles to catalyze selective hydrogenation of cinnamaldehyde,in order to obtain excellent catalytic activity,the MOFs structure was designed more accurately.A series of double-shell hollow nanospheres Void@Ui O-66-NH₂@Pt@Ui O-66-X(X=H,NH₂,Br,NO₂)catalysts with different morphologies were successfully synthesized.In addition,we modified the hollow MOFs and introduced the homogeneous catalyst with high activity into the MOFs to obtain the hollow nano-sphere Void@Ui O-66-I catalyst,which was used to catalyze the cycloaddition reaction of CO₂,and compared the catalytic activity with the solid MOFs functionalized of quaternary ammonium.Part I:Using SPS nanospheres(sulfonated polystyrene nanospheres)as templates,a layer of Ui O-66-NH₂was self-assembled on its surface,Pt nanoparticles were loaded onto Ui O-66-NH₂ by ordinary impregnation method.Then the terephthalic acid containing different functional groups and zirconium ions were used to grow a layer of Ui O-66-X(X=H,NH₂,Br,NO₂)in the outer layer.Finally,we used DMF to remove the template,a series of double-shell hollow nano-sphere catalysts(Void@Ui O-66-NH₂@Pt@Ui O-66-X)with different morphologies were obtained and used for selective hydrogenation of cinnamaldehyde.The catalyst Void@Ui O-66-NH₂@Pt@Ui O-66-NO₂ showed the best catalytic activity and good cycle stability with the morphology of porous and loose shell.Part II:Using SPS nanospheres as a template,a layer of Ui O-66-NH₂ was self-assembed on the surface of template.Then,Ui O-66-NH₂had a quaternization reaction with iodoethanol,so hydroxy functionalized quaternary ammonium salts were introduced into MOFs.Finally,the template was removed with DMF to get the hollow nanospheres Void@Ui O-66-I catalyst,and it was used in the CO₂ cycloaddition reaction to evaluate its activity and selectivity.Compared with solid Ui O-66-I,the Void@Ui O-66-I catalyst exhibited better catalytic activity because of the large volume of cavities,which can accelerate the mass transfer rate.