Study On The Construction Of Fiber Ionic Microenvironment And Its Utilization For CO₂ Fixation

Along with the development of industrialization,leading to massive burning of fossil fuel,the concentration of carbon dioxide（CO₂）in the atmosphere increases rapidly beyond the natural limits of ecosystems.CO₂ is one of the most important greenhouse gases,which brings climate change and environmental problems,thus restricts human development.Capture and utilization of CO₂ which is an abundant,non-toxic and renewable carbon resource is,therefore,essential for the solution of resource shortage and environmental problems.The cyclization reaction of CO₂ is a widespread concern because it meets the requirements of green chemistry.A series of quaternary ammonium salt functionalized fiber PAN_T-RF-X were prepared by amination,quaternization and ion exchange with different anions.The successful grafting of quaternary ammonium salt moieties on the fiber surface was proved by elemental analysis,infrared spectrum and scanning electron microscope,etc.It was suggested that ionic microenvironment was constructed inside the surface layers of the fiber.The effect of the ionic microenvironment on the cyclization of CO₂ with epoxides was investigated.After screening the optimal catalyst,it was found that a small amount（0.5 mol%）of fiber catalyst PAN_{T-Ud A}F-I with quaternary ammonium alkyl chain of 11 carbon atoms containing carboxyl and I^–as anion had the most satisfactory catalytic performance for cyclization reaction of CO₂with epichlorohydrin under mild conditions（80 ^oC,0.1 MPa）.Moreover,the fiber catalyst also has good applicability to other epoxides,the yield range in 24–99%.The PANT-Ud AF-I could be conveniently separated by filtration and showed good recyclability and durability till the 4th cycle.A new synergistic X^–catalytic mechanism is confirmed where the ionic micro-environment plays a crucial role to stabilize the ionic intermediate and lower the activation energy of the reaction,which provides a new basis for the design of green and efficient catalysts in the future.