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采用了适当的衔接手法，层次清晰；文中词汇使用灵活，高级词汇积累做的很棒，但拼写错误要注意；作者句法知识掌握的不够好，可适当增加从句的使用。
Carbon dioxide (CO2) is considered to be one of the main greenhouse gases resulted from human activities. The emission of CO2 at an accelerating rate in the atmosphere is causing global warming and climate change [1]. In fact, CO2 is not only the main greenhouse but also the most abundant carbon resource on earth. In recent decades, the conversion of CO2 into useful chemicals has attracted more and more attention in organic chemistry. CO2 is believed to be a promising alternative for toxic and hazardous raw reagents including phosgene, isocyanate and carbon monoxide which are generally employed in the conventional synthesis of cyclic carbonates, cyclic carbamates and cyclic ureas.Greener processes for the reactions involving CO2could be expected due to its non-toxic, non-flammable, inexpensive and available properties [2]. Carbonates [3], urea derivatives [4], formates [5] and polycarbonates [6] have been efficiently obtained via the reaction of CO2 with compounds including hydrogen, alkenes, acetals, epoxides, amines, phenol and carbon-carbon unsaturated compounds [7–9]. The conversion of CO2 presents significant challenges since the nature of CO2 is highly oxidized and thermodynamically stable [10]. As a result, most of the works related to the conversion of CO2 generally focus on developing effective catalytic systems [4]. A variety of homogenous catalysts such as salen-complexes, metal oxides and Lewis acids have been employed [3,4,11] but few effective heterogeneous systems were developed so far. A variety of investigations have been performed on the synthesis of carbonates via the coupling of CO2 with epoxide due to the atom economy process and high selectivity [12,13]. The synthesis of styrene carbonate (SC) via the coupling reaction of CO2 with styrene oxide (SO) is one of the noticeable ways. Homogeneous catalytic systems including salen-complexes [14,15], co-catalyst composed of Lewis acid, quaternary ammonium salt and/or ionic liquid have been developed [16–18]. Supported and/or anchored catalysts raise more and more interest since it is considered to be one of the most effective ways to eliminate the problems of difficult isolation and separation suffered from homogeneous catalytic systems [19]. In the presence of homogeneous n-Bu4NBr, acetylacetonates grafted solely on starch revealed stable and recyclable catalytic performance for the coupling reactions of CO2with epoxides to produce cyclic carbonates in excellent yield [20] but the chemically modified process for starch is complicated and expatiatory. Recently, homogeneous catalysts/reagents supported on magnetic nanoparticle Fe3O4 (MNPs-Fe3O4) have been developed as effective and recyclable catalyst for a number of reactions including hydrolysis, hydrogenation, oxidation, carbon-carbon coupling and reduction [2,21–24]. We have developed a heterogenized catalytic system by supporting simple Lewis acids on MNPs-Fe3O4 combined with MCM-41 (Fe3O4@MCM-41) for the synthesis of SC from SO and CO2 by adding quaternary ammonium salt into the reaction system directly [25]. Surprisingly, the as-prepared catalyst exhibits similar catalytic activity compared to that of homologous catalyst and excellent recyclability during 5 runs. However, only one of the components contained in co-catalyst was supported since the loading of active species from Lewis acid is very high, in which optimal Zn loading of 14.9 wt.% was required. Further supporting quaternary ammonium salt led to the impossibility in separation by an external magnet and destruction in the structureof support due to relatively low content of Fe3O4 and MCM-41 resulted from high content of active species. Based on the previous work [25], it is expected to develop a binary supported catalyst to replace single component supported catalyst so that the co-catalyst could be recovered together. To keep the structure and magnet of mixed support Fe3O4@MCM-41, this work aims to develop an effective and recyclable binary supported catalyst by reducing the loading of metal active species first. It has been reported that Cu(acac)2 is effective for the direct synthesis of valuable SC from CO2 and SO [26]. So Cu(acac)2 was selected as an alternative for Lewis acid employed in our previous work [25]. Both the metal active species and quaternary ammonium salt were supposed to support on Fe3O4@MCM-41. The catalytic performance of the as-prepared binarysupportedcatalyst was investigated by varyingkinds and amounts of catalyst, reaction conditions including pressure of CO2, reaction temperature and time. Cu(acac)2/n-Bu4NBr/Fe3O4@MCM-41 was also recovered and reused to evaluate recyclable performance without further treatment.
