Abstract To optimize the synergistic effects among hydrogen bond donors, halogen anions and basic sites, we synthesized a series of graphene oxide (GO) materials multi-functionalized with silanol group, multi-cationic quaternary ammonium salt and tertiary amine in a one-pot approach. Hexamethylenetetramine which is cheap and rich with tertiary amine was used as precursor. As characterized by elemental analysis and X-ray photoelectron spectroscopy, the loading of quaternary ammonium salt and tertiary amine was up to 2.56 and 1.84 mmol/g, respectively. This is the first time that a multi-functionalized GO (MF-GO) enriched with multi-cationic quaternary ammonium salt was prepared and used for the cycloaddition of CO 2 towards epoxides under mild conditions (90 °C, 2 MPa and 4 h) with high efficiency (TOF = 46.1 h −1 ) without the need of a solvent and a co-catalyst. The advantage of the combined use of the “multi-cationic approach” and “multi-synergetic strategy” was illustrated by comparing the performance of MF-GO with those of the GO samples that are endowed with different functional groups. A plausible mechanism is proposed for the cycloaddition reaction over MF-GO. Moreover, the MF-GO catalyst can be easily separated and reused for at least five times without significant loss of activity.

中文翻译：

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GO与多阳离子ILs的多功能化作为温和条件下CO 2 环加成的高效无金属催化剂

摘要 为了优化氢键供体、卤素阴离子和碱性位点之间的协同效应，我们以一锅法合成了一系列硅烷醇基、多阳离子季铵盐和叔胺多功能化的氧化石墨烯（GO）材料。 . 使用廉价且富含叔胺的六亚甲基四胺作为前体。通过元素分析和X射线光电子能谱表征，季铵盐和叔胺的负载量分别高达2.56和1.84 mmol/g。这是首次制备富含多阳离子季铵盐的多功能化GO（MF-GO），并用于在温和条件（90°C、2 MPa和4 h）下将CO 2 环加成成环氧化物具有高效率（TOF = 46。1 h -1 ) 无需溶剂和助催化剂。通过比较 MF-GO 与具有不同官能团的 GO 样品的性能，说明了“多阳离子方法”和“多协同策略”结合使用的优势。为MF-GO上的环加成反应提出了一种合理的机制。此外，MF-GO催化剂可以很容易地分离并重复使用至少五次而不会显着损失活性。