The Synthesis Of Imidazolium Functionalized Metal-Organic Materials And Their Applications In Adsorption And Catalysis

With the rapid development of morden society,environmental problems including water pollution and excessive amount of CO2 released in the atmosphere are becoming more and more serious.It is necessary to develop new materials and new technologies to reduce pollution.Imidazolium based ionic liquids composed of imidazolium cations and anions are known as green solvents,which is a kind of potential metarials for reducing pollution.Imidazolium based ionic liquids have attracted extensive attentions in extraction,catalysis and electrochemistry for their low vapour,tunable structures,high ionic conductivity and stability.However,imidazolium ionic liquids usually suffer from strong water imbibition,high viscosity,low mass transfer rate and non-recyclability.Herein,we designed and prepared a series of imidazolium functionalized cationic materials through incorporating imidazolium groups into metal-organic materials.These materials not only have the advantages of imidazoulium groups,but also possess good regeneration ability.The main content of this thesis covers the sorption of Cr2O72-anions and catalytic conversion of CO2 by these imidazolium functionalized matel-organic materials.The contents are as below:(1)In the first part,a mesoporous cationic Cr based metal-organic framework(FJI-C11)was synthesized with imidazolium functionalized ligands and CrCl3 via hydrothermal synthesis with mixed-solvents.Due to the strong Cr-O bond,FJI-C11 shows good thermal and chemical stability.FJI-C11 could be stable up to 220? and in qauoeus solution with a wide pH value range from 1 to 10.Thanks to the uncoordinated Cl-anions in the pores,FJI-C11 can adsorb the toxic anions such as Cr2O72-through ion-exchange mechanism.In addition,mesoporous FJI-C11 can provide larger pores for mass transfer and thus increase the Cr2O72-adsorption rate.FJI-C11 can adsorb 95%Cr2O72-in just 3 min with anuptake capacity of 321 mg-g-1.Furthermore,FJI-C11 also shows good selectivity and regeneration ability,which make FJI-C11 a potential material for the capture of Cr2O72-from wastewater.(2)In the second part,three metal-organic polyhedra(ImBDC-Zr,ImBPDC-Zr,ImTPDC-Zr)were constructed by the self-assembly of three different imidazolium functionalized dicarboxylic ligands((Cl)Im-H2Ln,n=1,2,3)and trinuclear zirconocene clusters.Single-crystal X-ray diffraction analysis reveals that these MOPs have similar capsule-shaped structure with V2E3(V=vertex and E=edge)topology.ImBDC-Zr and ImBPDC-Zr show good stability based on the analyses by powder X-ray diffraction(PXRD),thermogravimetric analysis(TGA)and mass spectrum(MS).However,ImTPDC-Zr is not stable because its large cavity is inclined to structural collapse.In addition,ImBDC-Zr and ImBPDC-Zr have good CO2 adsorption uptake.Meanwhile,the coexistence of acid sites(-OH)in trinuclear zirconocene clusters and nucleophilic Cl-anions endow ImBDC-Zr and ImBPDC-Zr with the ability to catalyze the cycloaddition reaction of CO2 with epoxides into cyclic carbonates in mild conditions.(3)In the third part,we developed a facile ion-exchange strategy to fabricate a MOF-based porous liquid(Im-UiO-PL)through replacing the Cl-anions on the surfaces of imidazolium functionalized MOF(Deim-UiO-66)by poly(ethylene glycol)tailed sulfonate(PEGS),which successfully endow Deim-UiO-66 with fluidity.Meanwhile,hindered PEGS are too large to enter the cavities of Deim-UiO-66,which leaveslm-UiO-PL with permanent porosity.The fluidity and porosity of Im-UiO-PL are demonstrated by a series of characterizations and theoretical calculations.However,the cavities of Im-UiO-PL are accessiable for CO2 molecules.Thus,Im-UiO-PL shows ca.14 times larger CO2 adsorption uptake capacities than that of pure PEGS because Im-UiO-PL can provide more space to store CO2 molecules.Furthermore,the stored CO2 in Im-UiO-PL could be slowly released and utilized to synthesize cyclic carbonates in the presence of TBAB at 1 bar.