Preparation Of Poly（Ionic Liquid）s-Supported N-heterocyclic Carbene Silver Complex For The Cycloaddition Of CO₂

CO₂ as the main greenhouse gas on the earth,a large amount of CO₂ emissions has caused some environment problems.Nevertheless,CO₂ is an aboundant,economic,nontoxic and renewable C1 feedstocks,which can be utilized as raw material to synthesize a variety of chemicals.The synthesis of cyclic carbonates via the cycloaddition reaction of CO₂ and epoxides is one of the most efficient ways for chemical fixation of CO₂.Poly（ionic liquid）s（PILs）with high stability,excellent durability,easily tunable structure,easily separation and recovery have been widely used as catalysts or catalyst supports.Ag-NHCs were easily prepared from cheap starting materials and insensitive to air and moisture,which makes them exhibited unique advantages for transformation of CO₂.This dissertation focuse on the poly（ionic liquid）s with nucleophilic halogen anion and Ag-NHCs with Lewis acid site,a series of poly（ionic liquid）s-supported N-heterocyclic carbene silver complex were prepared and then applied to catalyze the cycloaddition reactions of epoxides and CO₂.The main contents are abtained as follows:1.A concise introduction of significance of CO₂ cycloaddition reaction,and the researching advances of PILs and Ag-NHCs.2.A series of poly（ionic liquid）s-supported N-heterocyclic carbene silver complex（Poly（Ag-NHC/IL））with different alkyl substituents were prepared through radical co-polymerization of 3-alkyl-1-vinylimidazolium bromide（VI-C4,6,8）,Ag-NHCs monomers and DVB using AIBN as initiator in acetonitrile.Both the structures of polymers characterized by NMR spectra,¹³C MAS NMR spectra,FT-IR spectra,N₂-isotherm,SEM,TG and ICP-AES.Through adjusting the molar ration of Ag-NHCs to 3-alkyl-1-vinylimidazolium bromide（VI-C4,6,8）,Poly（Ag-NHC/IL）have maximum surface area is 140 m²g^-1.3.Poly（ionic liquid）s-supported N-heterocyclic carbene silver complexes were applied as catalyst for the cycloaddition of CO₂ and epoxides.The influences of the type and amount of catalyst,the reaction temperature,the reaction time and CO₂pressure on the reaction have been systemically investigated.These catalysts could efficiently catalyze the cycloaddition reaction of CO₂ and epoxides with silver as the Lewis acid site and a bromine anion as a nucleophilic agent working in a cooperative way,the yields of cyclic carbonates were reached 97%under mild conditions.Furthermore,the catalyst can be easily separated and recovered without any significant loss of catalytic activity after five times.For comparison,the synergistic effect in homogeneous system with 3-alkyl-1-vinylimidazolium bromide（VI-C4,6,8）and Ag-NHCs were also studied.The activity of the catalyst increased with an increase of the Br^-to Ag molar ration and reached the maximum at a Br^-to Ag molar ration of 4.4.A series of facile and stable Ag-NHCs have been synthesized,and the structures of Ag-NHCs were characterized by NMR spectra.The Ag-NHCs were applied as catalysts for the cycloaddition of CO₂ and epoxides,the influences of the type and amount of catalyst,the reaction temperature,the reaction time and CO₂pressure on the reaction have been systemically investigated.The results showed that the optimum reaction conditions are abtained as follows:1 mmol%AgNHC-2,110℃,3 h,1 MPa CO₂,the cycloaddition of CO₂ and epoxides obtained the highest catalytic activity with the yields of cyclic carbonates reached 96%and 100%selectivity.