L.W. Wijayanti et al. Proceeding of The International Seminar on Chemistry 2008 (pp. 356-362) Jatinangor, 30-31 October 2008 356 Ionic liquids in green chemistry: catalytic reaction of cyclic carbonates formation and CO 2 capture employing ionic liquids Lucia Wiwid Wijayanti 1 , Jelliarko Palgunadi 2 *, Probo Bharoto Putro 1 1 Faculty of Pharmacy, Sanata Dharma University, Kampus III Paingan, Maguwohardjo, Depok Sleman, Yogyakarta 55281, Indonesia. Telp. +62-274-883037; Fax. +62-274-886529 2 Green Chemistry Lababoratory, Kyung Hee University, 1-Hoegidong, Dongdaemungu, Seoul 130-701, Rep. of Korea *e-mail: jelliarko@yahoo.com Abstract There is a considerable attention to reduce the carbon dioxide emission or utilize this gaseous waste as an industrial feedstock. Ionic liquids (ILs) which are liquid salts below 100 °C are known as “green” designer solvents and are due to their unique properties such as, no measurable vapor pressure, tunable physical and chemical properties, and high thermal stability may open future applications in many fields. Highly active zinc tetrahalide-ionic liquid adduct was successfully employed to catalysis the coupling reaction of various epoxides with CO 2 to produce selectively the corresponding cyclic carbonates with high yield. Accessible and relatively cost effective room temperature ionic liquids were also synthesized and tested for the CO 2 capture. It was found that ionic liquid can absorb CO 2 physically and can easily be regenerated under a reduced pressure, thus minimizing the energy consumption for recycling compared to a conventional amine-based aqueous solution. Keywords: Absorption, carbon dioxide, cyclic carbonate, ionic liquid, zinc tetrahalide Introduction The transformation of CO 2 into alkylene carbonates by the coupling reaction with epoxides has received much attention with regard to the utilization of CO 2 , a gas responsible for global warming [1–4]. Alkylene carbonates are used as raw materials in a wide range of chemical reactions: the production of ethylene glycol esters, hydroxyalkyl derivatives, carbamates, alkylene sulfides, polyurethanes, polyesters and polycarbonates [5–7]. Recently, there is an increasing demand for cyclic carbonates as solvent for polymer and gel electrolytes in secondary and fuel-cell batteries [8,9]. Accordingly, a substantial literature on the catalyst development and mechanism for the coupling reactions has been reported [10–12]. The use of transition metal halide catalysts along with t-alkyl ammonium halide or alkali metal halide has been shown to be a highly active combination for promoting the coupling reactions, where the halide ligands act as nucleophiles [13–16]. The catalytic systems composed of transition metal halide (AlCl 3 , NiCl 2 , MoCl 5 , etc.) and Lewis base such as amines or phosphines have been employed in the selective formation of cyclic carbonates [17]. Zinc(II) complexes have also been used as catalysts, owing to their high activity in the cyclization and copolymerization of CO 2 and epoxides [18–21]. Recently, imidazolium-based ionic liquids have been employed as reaction media and/or catalysts for the coupling reactions but the productivity were not high enough for the practical purposes even at elevated temperatures [22]. During the course of our studies on the development of active catalysts for the coupling reaction, we have found that the catalytic activities of imidazolium-based ionic liquids can be drastically enhanced by the co-presence of zinc halides due to the formation of highly active species, imidazolium zinc tetrahalides [23]. Herein, we report the synthesis, characterization and reactivities of a series of imidazolium zinc tetrahalide complexes of the general formula (1-R-3- methylimidazolium) 2 - ZnX a Y 4-a (R:CH 3 , C 2 H 5 , n- C 4 H 9 , CH 2 C 6 H 5 ;X,Y: Cl, Br; a: 0, 2, 4) for the coupling reactions of various alkylene oxide with CO 2 as well as the single crystal X-ray diffraction analysis of (1,3-dimethylimidazolium) 2 ZnCl 2 Br 2 . We also report another research work that performed solubility of CO 2 in ionic liquids. The finding of remarkable solubility of CO 2 in room- temperature ionic liquids [27] and also driven by the increasing demands on the more environmentally friendly CO 2 absorbent systems which only involving physical interactions have attracted many research groups to investigate the utilization of room- temperature ionic liquids (RTILs) in the CO 2 separation. The promising application of non-volatile ISBN 978-979-18962-0-7