The Design And Synthesis Of Functionalized Ionic Liquids For Efficient Carbon Capture

Recently,the emmision of carbon dioxide（CO₂）during to the rapid development of industry has attracted a wide attention for their intribution to climate change.Ionic liquids（ILs）have been considered as pontential CO₂ absorbent because of their unique properties.However,the capture of CO₂ in ILs have drawbacks such as limited absorption-site and high viscosity（≥100 cP）,resulting in low capacity（≤0.10 g/g）and low absorption kinetics.Thus,we proposed a new strategy for the absoprtion of CO₂ through multi-sites interaction to enhance CO₂ capacity,and designed effective hybrid solvents for CO₂ capture to improve absorption kinetics.Besides,CO is an important industrial gas feedstock for C1 chemistry,research into the removal,purification,and utilization of CO is very important in chemical industry fields.We present a new method for significantly enhanced CO capture by several carbanion-functionalized ILs by making use of supernucleophilicity of carbanions.To the best of our knowledge,this is the first example for CO chemisorption by pure ILs.Firstly,multi-molar absorption of CO₂ in amino acid ionic liquids is reported by activating a carboxylate group in aminopolycarboxylate-based amino acid ionic liquids.It was illustrated that introducing an electron-withdrawing site to amino acid anions could reduce the negative inductive effect of the amino group while simultaneously activating the carboxylate group to interact with CO₂ very efficiently.An extremely high absorption capacity of CO₂（1.69 mol mol-1）in aminopolycarboxylate-based amino acid ionic liquids was thus achieved.It breaks the upper limit of the equimolar capture of CO₂ in amino acid ionic liuqids.In addition,excellent reversible process by those ILs can provide a potential alternative for CO₂ capture.Amino acid ionic liquids（AAILs）are chemical solvents with high reactivity to CO₂.However,they suffer from drastic increase in viscosity upon the reaction with CO₂,which significantly limits their application in the industrial capture of CO₂.Thus,1-ethyl-3-methylimidazolium acetate（[emim][Ac]）which also exhibits chemical affinity to CO₂ but low viscosity,and its viscosity does not increase drastically after CO₂ absorption,was proposed as the diluent for AAILs to fabricate hybrid materials.The AAIL+[emim][Ac] hybrids were found to display enhanced kinetics for CO₂ absorption,and their viscosity increase after CO₂ absorption are much less significant than pure AAILs.More importantly,owing to the fact that [emim][Ac] itself can absorb large amount of CO₂,the AAIL+[emim][Ac] hybrids still have high absolute capacities of CO₂.Such hybrid materials consisting of a chemical solvent plus another chemical solvent are believed to be a class of effective absorbents for CO₂ capture.CO is an important industrial gas feedstock for C1 chemistry.Then it is very important to study on CO separation and ultilation.A novel method for highly efficient and reversible capture of CO in carbanion-functionalized ionic liquids（ILs）via C-site interaction is reported.It was demonstrated that the carbanion in ILs,because of its supernucleophilicity,could absorb CO efficiently.As a result,an relatively high absorption capacity for CO（up to 0.046 mol mol-1）was achieved under ambient conditions,over 20 times more than CO solubility in a commonly used IL [Bmim][Tf2N]（2×10-3 mol mol-1）.The results of quantum mechanical calculations and spectroscopic investigation confirmed that the chemical interaction between C-sites in the carbanion and CO resulted in the superior CO absorption capacities.Furthermore,the subsequent conversion of captured CO to valuable chemicals with good reactivity was also realized through the alkoxycarbonylation reaction under mild conditions.In summary,in this thesis,a series of novel ionic liquids were designed and applied for carbon capture to test their capacity and reversibility.The absorption mechanism was also studied systematically through spectroscopic investigations and quantum chemical calculations.We believe that our work can provide a new way of designing novel absorbent and lay a foundation for gas separation using ILs.