Efficient acid-base bifunctional catalysts for the fixation of CO(2) with epoxides under metal- and solvent-free conditions

ChemSusChem. 2011 Apr 18;4(4):502-7. doi: 10.1002/cssc.201000305. Epub 2011 Jan 27.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carbon Dioxide / chemistry*
  • Catalysis
  • Epoxy Compounds / chemistry*
  • Green Chemistry Technology
  • Hydrogen-Ion Concentration
  • Lewis Acids / chemistry
  • Lewis Bases / chemistry
  • Metals / chemistry
  • Solvents / chemistry

Substances

  • Epoxy Compounds
  • Lewis Acids
  • Lewis Bases
  • Metals
  • Solvents
  • Carbon Dioxide