Functionalized Poly（ionic Liquid）s For The CO₂ Conversion Into Cyclic Carbonates

The conversion of CO2,greenhouse gas,into high-value chemicals is an economically and effective way to reduce the CO2 emission.Among all the methods,the cycloaddition reaction of CO2 and epoxides to obtain cyclic carbonates is a green route to achieve this goal,which comforms to the principle of atom economy.The development of high activity and high stability catalysts is the key point to this technical route.In order to solve the disadvantage of complex separation of homogeneous catalysts and poor activity of hterogeneous catalysts,the hydrogen bond donor functionalized poly(ionic liquid)s and multi-site poly(ionic liquid)s with high activity and stability were developed in this paper,respectively.The main work and innovative achievement includes the following conclusions.1.A series of functionalized poly(ionic liquid)s(HPILs)with 2-hydroxyethyl methacrylate as hydrogen bond donor were designed and synthesized.Through regulating the molar ratio of ionic liquid monomers,hydrogen bond donor and cross-linker,the best catalyst was seized from all HPILs.The HPILs were successfully synthesized verified by NMR,FT-IR,EA,XPS etc.According to the experiments,when the molar ratio of ionic liquid and HEMA was 1:1.5,the poly(ionic liquid)HPIL-7 could achieve the best catalytic performance.The yield of propylene carbonate(PC)reached 94%(at 105℃,2 MPa CO2,3 h),which even approached bulk ionic liquids(PC yield 95%).In addition,the interactions of hydrogen bond donor and ionic liquid with reactants were preliminarily studied according to NMR spectra and DFT simulations.Therefore,a possible hydrogen bond donor and nucleophilic anion synergetic catalytic mechanism was proposed.2.A series of multi-site poly(ionic liquid)s were prepared by thiol-ene click reaction with dual-cation ionic liquids and trithiocyanuric acid(TTCA)under UV irradiation,aiming at addressing the problems of low catalyst activity and complicated preparation method.By adjusting the influence factors such as the presence of photoinitiator,solvent additive and illumination time,it was found that pPILs could be prepared quickly without the presence of initiator,and was not affected by the environmental factors such as oxygen and water.The P[VImBMBP]2Cl2-TTCA(heptane),which was prepared by[VImBMBP]2Cl2 and TTCA in the presence of heptane,could effectively catalyze the reaction.The PC yield was 98.4%at 100℃,co-catalyst free and solvent free conditions.Cyclicity test and FT-IR analysis showed that the activity of the catalyst insignificantly decrease and the structure remained unchanged after 6 cycles.In addition,FT-IR and X-ray photoelectron spectroscopy analysis revealed that the adsorbed water molecules existed in the structure of the pPILs.By DFT simulation calculations and NMR analysis,a possible mechanism of hydrogen bond interaction and nucleophilic anions synergistic catalytic reaction was proposed.