Efficient synthesis of cyclic carbonates under atmospheric CO2 by DMAP-based ionic liquids: The difference of inert hydrogen atom and active hydrogen atom in cation
Efficient synthesis of cyclic carbonates under atmospheric CO2 by DMAP-based ionic liquids: The difference of inert hydrogen atom and active hydrogen atom in cation
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DOI：
10.1016/j.gce.2022.06.001
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发表时间：
2022-06
影响因子：
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通讯作者：
Zhengkun Zhang;Jinya Li;Guanyao Yu;Chao Zeng;Menglong Wang;Susu Huang;Li Wang;Jinglai Zhang-Jinglai-Zhan
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文献类型：
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作者：
Zhengkun Zhang;Jinya Li;Guanyao Yu;Chao Zeng;Menglong Wang;Susu Huang;Li Wang;Jinglai Zhang-Jinglai-Zhan
二氧化碳（CO2）和环氧化物的偶联反应是实现碳平衡的最有效途径之一。然而，如何在温和的条件下，特别是在大气压下实现这一目标，仍然是一个令人困惑的问题。设计并合成了三种新型离子液体（IL）：[DMAPBrPC][TMGH]、[DMAPBrPC][DBUH]和[DMAPBrPC][BTMA]。它们都对标题反应表现出优异的催化活性，在大气 CO2 压力和 60 °C 下实现了超过 96.6% 的产率。有趣的是，与其他两种在阳离子中具有质子氢原子和相同阴离子的离子液体相比，在阳离子中具有惰性氢原子的[DMAPBrPC][BTMA]表现出优异的催化活性。 [DMAPBrPC][TMGH]和[DMAPBrPC][DBUH]中的活泼氢原子会阻碍-COO-基团吸收CO2，这对反应是不利的。此外，[DMAPBrPC][TMGH]和[DMAPBrPC][DBUH]中的强氢键会降低Br−阴离子的亲核能力，导致催化性能较差，密度泛函理论（DFT）计算进一步证实了这一点。当与合适的阴离子结合时，不含活性氢原子的阳离子也可用于设计具有优异催化特性的离子液体。
The coupling reaction of carbon dioxide (CO2) and epoxides is one of the most efficient pathways to achieve the carbon balance. However, to accomplish it under the mild conditions, especially under the atmospheric pressure, is still a perplexing problem. Three novel ionic liquids (ILs), [DMAPBrPC][TMGH], [DMAPBrPC][DBUH], and [DMAPBrPC][BTMA], are designed and synthesized. All of them display the excellent catalytic activity for the title reaction achieving the yield over 96.6% under the atmospheric CO2pressure at 60 °C. Interestingly, [DMAPBrPC][BTMA] with the inert hydrogen atom in cation exhibits the superior catalytic activity as compared to other two ILs with the protic hydrogen atom in cation along with the same anion. The active hydrogen atom in [DMAPBrPC][TMGH] and [DMAPBrPC][DBUH] would impede the –COO−group to absorb CO2, which is an unfavorable item for the reaction. Moreover, the strong hydrogen bond in [DMAPBrPC][TMGH] and [DMAPBrPC][DBUH] would lessen the nucleophilic ability of Br−anion resulting in the inferior catalytic performance, which is further confirmed by the density functional theory (DFT) calculations. The cation without the active hydrogen atom could also be employed to design the ILs with the excellent catalytic feature when it is combined with the suitable anion.