Efficient Acid–Base Bifunctional Catalysts for the Fixation of CO2 with Epoxides under Metal- and Solvent-Free Conditions

Authors

  • Dr. Jian Sun,

    1. State Key Laboratory of Multiphase Complex System, Institute of Process Engineering, Chinese Academy of Sciences, 100190 Beijing (PR China), Fax: (+86) 10-8262-7080
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  • Dr. Lijun Han,

    1. State Key Laboratory of Multiphase Complex System, Institute of Process Engineering, Chinese Academy of Sciences, 100190 Beijing (PR China), Fax: (+86) 10-8262-7080
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  • Dr. Weiguo Cheng,

    1. State Key Laboratory of Multiphase Complex System, Institute of Process Engineering, Chinese Academy of Sciences, 100190 Beijing (PR China), Fax: (+86) 10-8262-7080
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  • Dr. Jinquan Wang,

    1. State Key Laboratory of Multiphase Complex System, Institute of Process Engineering, Chinese Academy of Sciences, 100190 Beijing (PR China), Fax: (+86) 10-8262-7080
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  • Prof. Xiangping Zhang,

    1. State Key Laboratory of Multiphase Complex System, Institute of Process Engineering, Chinese Academy of Sciences, 100190 Beijing (PR China), Fax: (+86) 10-8262-7080
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  • Prof. Suojiang Zhang

    Corresponding author
    1. State Key Laboratory of Multiphase Complex System, Institute of Process Engineering, Chinese Academy of Sciences, 100190 Beijing (PR China), Fax: (+86) 10-8262-7080
    • State Key Laboratory of Multiphase Complex System, Institute of Process Engineering, Chinese Academy of Sciences, 100190 Beijing (PR China), Fax: (+86) 10-8262-7080
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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 CO2 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 [{(CH2)3COOH}2im]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 CO2 into value-added chemicals.

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