Low-Cost Polymer-Supported Quaternary Ammonium Salts as High-Efficiency Catalysts for Cycloaddition of CO 2 to Epoxides Yuan-Yuan Zhang • Lang Chen • Shuang-Feng Yin • Sheng-Lian Luo • Chak-Tong Au Received: 7 August 2012 / Accepted: 15 September 2012 / Published online: 26 September 2012 Ó Springer Science+Business Media New York 2012 Abstract Polystyrene grafted with quaternary ammonium salts were obtained by direct quaternarization of chlorome- thylated polystyrene with N,N-dimethylethylamine, N,N- dimethylglycine (denoted as PS-QNS and PS-CQNS, respectively). These two polymer-supported ionic liquids were found to show high catalytic efficiency towards the cycloaddition of CO 2 to epoxides. The effects of catalyst amount, reaction temperature, initial CO 2 pressure, and reaction time on the yield of cyclic carbonates were investi- gated systematically. Under the optimal reaction conditions (150 °C, initial CO 2 pressure 2.0 MPa and 5 h), propylene carbonate yield and selectivity in the cycloaddition of CO 2 to propylene oxide over PS-CQNS were 96.2 and 99.3 % whereas those over PS-QNS were 97.9 and 99.5 %, respec- tively. It was observed that the reusability of PS-QNS was excellent. From the viewpoint of industrial application, PS-QNS is attractive in terms of catalytic efficiency, cost and simplicity in preparation. Keywords Polymer-supported quaternary ammonium salts  Carbon dioxide  Epoxide  Cyclic carbonate 1 Introduction Carbon dioxide is a major green-house gas. Motivated by the idea of environmental protection, scientists are paying much attention to the fixation of CO 2 . An important reaction is the synthesis of five-membered cyclic carbonates via the cyclo- addition of CO 2 to epoxides. The reaction is desirable because of three main reasons: (i) reactants are cheap (ii) atom utili- zation is high, and (ii) generation of by-product is low [1, 2]. Besides, five-membered cyclic carbonates are important chemicals and intermediates that are extensively applied in organic syntheses for the production of pharmaceuticals and fine chemicals [1, 3, 4]. They can also be used as aprotic polar solvents, electrolytic components of lithium secondary bat- teries, and cosmetics additive [5–7]. Up to now, many materials having been explored to catalyze the cycloaddition of CO 2 to epoxides, such as alkali metal salts [8, 9], organic bases [10, 11], metal oxides [12, 13], ion exchange resins [2], and modified molecular sieves [14]. So far, ionic liquids (ILs) containing imidazolium salts [15, 16], quaternary ammonium salts [17, 18], and quaternary phosphonium salts [19–21] have been used as catalysts for the synthesis of cyclic carbon- ates. In terms of separation, reusability, and cost effec- tiveness, the application of homogeneous catalysts has its limitation. Compared with homogeneous catalysts, heter- ogeneous catalysts could be easily separated and reused. In order to fabricate stable and reusable heterogeneous cata- lysts, ionic liquids were immobilized on solid materials such as magnetic nanoparticles [22] and inorganic materi- als [5, 23, 24], as well as on mesoporous materials such as SBA-15 and MCM-41 [25, 26]. However, as pointed out by Xiao et al. [23] and Dai et al. [26], due to leaching of ILs, there was decrease of catalytic activity, thus leading to poor reusability of catalysts. Another problem one should Y.-Y. Zhang  L. Chen  S.-F. Yin (&)  S.-L. Luo  C.-T. Au State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, Hunan, China e-mail: sfyin73@yahoo.com.cn; sf_yin@hnu.edu.cn C.-T. Au Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong, China 123 Catal Lett (2012) 142:1376–1381 DOI 10.1007/s10562-012-0909-y