Polymeric membranes either containing, or built from, ionic liquids (ILs) are of great interest for enhanced CO₂/light gas separation due to the stronger affinity of ILs toward quadrupolar CO₂ molecules and hence high CO₂ solubility selectivity. Herein, we report the development of a series of four novel anionic poly(IL)-IL composite membranes via a photopolymerization method for effective CO₂ separation. Interestingly, these are the first examples of anionic poly(IL)-IL composite systems in which the poly(IL) component has delocalized sulfonimide anions pendant from the polymer backbone with imidazolium cations as “free” counterions. Two types of photopolymerizable methacryloxy-based IL monomers (MILs) with highly delocalized anions (−SO₂–N⁽⁻⁾–SO₂–CF₃ and −SO₂–N⁽⁻⁾–SO₂–C₇H₇) and mobile imidazolium ([C₂ mim]⁺) countercations were successfully synthesized and photopolymerized with two distinct amounts of free IL containing the same structural cation ([C₂ mim][Tf₂N]) and 20 wt % PEGDA cross-linker to serve as a composite matrix. The structure–property relationships of the four newly developed anionic poly(IL)-IL composite membranes were extensively characterized by thermogravimetric analysis, differential scanning calorimetry, and X-ray diffraction. All of the newly developed anionic poly(IL)-IL composite membranes exhibited superior CO₂/CH₄ and CO₂/N₂ selectivities together with moderate CO₂/H₂ selectivity and reasonable CO₂ permeabilities. The membrane with an optimal composition and polymer architecture (MIL-C₇H₇/PEGDA_(20%)/IL_(1 equiv)) reaches the 2008 Robeson upper bound limit of CO₂/CH₄ due to the simultaneous improvement in permeability and selectivity (CO₂ permeability ∼20 barrer and αCO₂/CH₄ ∼119). This study provides a promising strategy to explore the benefits of anionic poly(IL)-IL composites to separate CO₂ from flue gas, natural gas, and syngas streams and open up new possibilities in polymer membrane design with strong candidate materials for practical applications.

中文翻译：

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量身定制的CO _2-阴离子聚（离子液体）复合膜的合成，表征和气体传输性能

包含离子液体（IL）或由离子液体（IL）构建的聚合物膜对于增强CO ₂ /轻气体分离具有极大的兴趣，因为IL对四极CO ₂分子的亲和力更强，因此具有较高的CO ₂溶解度选择性。在这里，我们报告通过光聚合方法有效的CO ₂的一系列四个新型阴离子聚（IL）-IL复合膜的发展分离。有趣的是，这些是阴离子聚（IL）-IL复合系统的第一个示例，其中聚（IL）组分具有离聚物磺化阴离子悬挂在聚合物主链上，并带有咪唑鎓阳离子作为“游离”抗衡离子。两种具有高度离域阴离子的可光聚合甲基丙烯氧基基IL单体（-SO ₂ -N ^（-）- SO ₂ -CF ₃和-SO ₂ -N ^（-）- SO ₂ -C ₇ H ₇）和移动咪唑鎓（[C ₂ mim] ⁺）抗衡阳离子成功合成，并与两种不同量的含有相同结构阳离子（[C ₂ mim] [Tf ₂ N]）和20 wt％PEGDA交联剂的游离IL光聚合，以用作复合基质。通过热重分析，差示扫描量热法和X射线衍射广泛表征了四种新开发的阴离子聚（IL）-IL复合膜的结构与性质之间的关系。所有新开发的阴离子聚（IL）-IL复合膜均显示出优异的CO ₂ / CH ₄和CO ₂ / N ₂选择性以及适度的CO ₂ / H ₂选择性和合理的CO₂磁导率。具有最佳组成和聚合物结构的膜（MIL-C ₇ H ₇ / PEGDA _（20％） / IL _{（1当量）}）达到2008年Robeson的CO ₂ / CH ₄上限，因为同时提高了渗透性和选择性（CO ₂渗透性〜20巴拉和αCO ₂ / CH ₄ ~119）。这项研究为探索阴离子聚（IL）-IL复合材料从烟气，天然气和合成气流中分离出CO ₂的益处提供了一种有前途的策略，并为在聚合物膜设计中提供了强大的实用候选材料开辟了新的可能性。