title: Efficient acid-base bifunctional catalysts for the fixation of CO(2) with epoxides under metal- and solvent-free conditions.
abstract: A series of acid-base bifunctional catalysts (ABBCs) that contain one or two Brønsted acidic sites in the cationic part and a Lewis-basic site in the anionic part are used as efficient catalysts for the synthesis of cyclic carbonates by cycloaddition of CO(2) to epoxides, without the use of additional co-catalyst or co-solvent. The effects of the catalyst structures and various reaction parameters on the catalytic performance are investigated in detail. Almost complete conversion can be achieved in 1 h for propylene oxide using [{(CH(2))(3)COOH}(2) im]Br under mild reaction conditions (398 K and 2 MPa). Furthermore, the catalyst can be recycled over five times without substantial loss of catalytic activity. This protocol is found to be applicable to a variety of terminal epoxides, producing the corresponding cyclic carbonates in good yields and high selectivities. A synergistic effect of the acidic and the basic sites as well as suitable hydrogen-bonding strength of ABBCs are considered crucial for the reaction to proceed smoothly. The activities of the ABBCs increase remarkably with increasing carboxylic-acid chain length of the cation. This metal- and solvent-free process thus represents an environmentally friendly process for BTC-catalyzed conversion of CO(2) into value-added chemicals.
authors.affiliation: State Key Laboratory of Multiphase Complex System, Institute of Process Engineering, Chinese Academy of Sciences, 100190 Beijing, PR China.
authors.forename: Jian
authors.initials: J
authors.lastname: Sun
authors.forename: Lijun
authors.initials: L
authors.lastname: Han
authors.forename: Weiguo
authors.initials: W
authors.lastname: Cheng
authors.forename: Jinquan
authors.initials: J
authors.lastname: Wang
authors.forename: Xiangping
authors.initials: X
authors.lastname: Zhang
authors.forename: Suojiang
authors.initials: S
authors.lastname: Zhang
mesh_terms: D002245:Carbon Dioxide / Q000737:chemistry*; D002384:Catalysis; D004852:Epoxy Compounds / Q000737:chemistry*; D055772:Green Chemistry Technology; D006863:Hydrogen-Ion Concentration; D058116:Lewis Acids / Q000737:chemistry; D058115:Lewis Bases / Q000737:chemistry; D008670:Metals / Q000737:chemistry; D012997:Solvents / Q000737:chemistry
chemical_list: D004852:Epoxy Compounds; D058116:Lewis Acids; D058115:Lewis Bases; D008670:Metals; D012997:Solvents; D002245:Carbon Dioxide