Carbon Dioxide Capture And Chemical Transformation By Task-specific Ionic Liquids And Its Derivatives

As the rapid development of industry,a large amount of CO₂ is emitted into the atmosphere,triggering a series of environmental problems.In order to reduce CO₂emissions,it is urgent to develop strategies for carbon dioxide capture,storage and utilization(CCSU),and the development of new absorbents is the key for CCSU.In this work,aiming at the development of new absorbents,a series of task-specific ionic liquids(ILs)and alternatives to ILs were designed,synthesized and applied to CO₂absorption.The absorption process,absorption enthalpy and absorption mechanism of different absorbents were systematically investigated.In addition,task-specific ILs were used in the synthesis of functionalized polycarbonates.The details are listed as follows:Firstly,task-specific IL was a research focus in CO₂ capture field,and a series of dual-functionalized ILs were designed and synthesized from the molecular level in this work.The dual-functionalized ILs exhibited excellent molar absorption.Even at low CO₂ partial pressures,the dual-functionalized ILs still maintained good absorption properties.As the reaction process of the dual-functionalized ILs and CO₂was exothermic,the saturated CO₂ capacity decreased with the increase of temperature.Besides,the dual-functionalized ILs exhibited lower absorption enthalpy of CO₂than aqueous MEA solution.Based on the results of experimental investigation,the IR spectra analysis,and Density functional theory(DFT)calculation,the corresponding absorption mechanism was put forward.Secondly,to comply with the concept of green chemistry and reduce the synthesis steps,two types of alternatives to ILs(CO₂ binding organic liquids(CO₂BOLs)and task-specific deep eutectic solvents(DESs))were synthesized.In order to overcome the volatile characteristics of lower alcohols and improve the stability of CO₂BOLs,a series of binary and ternary glycerol-based CO₂BOLs were synthesized.As is clear evidenced by the experimental and characterization results,the easy deprotonation property of glycerol directly contributed to the binding of CO₂.In order to further improve the stability of CO₂ absorbents,a series of new task-specific DESs were designed and synthesized based on the protic ionic liquid.Combinded experimental results with characterization,and DFT calculation,the combination of CO₂ by protonated superbase and neutral zwitterion was suspected to increase the absorption capacity.Besides,in both CO₂BOLs and ternary glycerol-based CO₂BOLs and task-specific DESs absorption systems,ionic liquids could served as an absorption medium to promote the mass transfer.Finally,CO₂ is considered as a valuable carbon source,especially in the copolymerization of CO₂ and epoxides to synthesize degradable aliphatic polycarbonates.In this work,a series of protic ionic liquids were synthesized and utilized as chain transfer agents in the copolymerization of CO₂ and propylene oxide(PO).It was interesting to note that the anion type of ionic liquid had a significant impact on the role of ionic liquids in the reaction process.Based on the results of experimental observations,along with ¹H NMR and MALDI-TOF-MS spectra,a mechanism for the copolymerization of CO₂ and PO in the presence of protic ILs was proposed.Moreover,the ion-containing polycarbonate studied in this work was amphiphilic,and could form nanoparticles in methanol with a narrow particle size distribution.