One important challenge in advanced gas separation membranes is breaking the trade-off effect between gas permeability and selectivity. Here, we developed a method by combining the debromination and thermal rearrangement (TR) techniques together to significantly enhance the gas separation properties of the resulting membrane for the first time. First, we designed a co-polyimide (DBOH) containing both hydroxyl and bromine (50/50) groups in the ortho position of the imide group. After thermal treatment at 450 °C, the TR and debromination happened simultaneously as proved by TG-MS, FT-IR and XPS results, the resulting DBPO showed a larger d-spacing (7.03–9.71 Å), a 18-fold enhanced BET surface area, and 2-fold improved in ultra-microporosity (<7 Å) than its DBOH precursor. Hence, DBPO demonstrated not only an over 100 times improved CO permeability (7933 76 Barrer) but also keep a high CO/CH selectivity of 31, and the overall performance surpassed the latest 2019 trade-off curve. Besides, wonderful anti-plasticization and mixed-gas separation properties were also observed for DBPO, which showed a CO permeability of 3324 Barrer and CO/CH selectivity of 14.7 even under the upstream CO/CH mixed-gas pressure of 435 psi (1 psi = 6894.8 Pa), outperforming the latest 2018 CO/CH mixed-gas upper limit. It showed 100 times improved CO permeability while maintain selectivity of DBPO is attributed to the significantly enhanced ultra-microporosity that increases the diffusion and solubility coefficient, whereas maintain their diffusion and solubility selectivity. Conclusively, the debromination coupled with TR provides a novel direction for designing advanced TR membranes.

中文翻译：

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通过同时脱溴和热重排显着增强膜的气体分离性能

先进气体分离膜的一项重要挑战是打破气体渗透性和选择性之间的权衡效应。在这里，我们开发了一种将脱溴和热重排（TR）技术结合在一起的方法，首次显着提高所得膜的气体分离性能。首先，我们设计了一种在酰亚胺基团的邻位同时含有羟基和溴（50/50）基团的共聚酰亚胺（DBOH）。经过 450 °C 热处理后，TR 和脱溴同时发生，TG-MS、FT-IR 和 XPS 结果证明，所得 DBPO 显示出更大的 d 间距（7.03–9.71 Å），BET 增强 18 倍比 DBOH 前​​体的表面积和超微孔隙率 (<7 Å) 提高了 2 倍。因此，DBPO不仅表现出超过100倍的CO渗透率提高（7933 76 Barrer），而且保持了31的高CO/CH选择性，整体性能超越了最新的2019年权衡曲线。此外，DBPO 还具有出色的抗塑化和混合气体分离性能，即使在上游 CO/CH 混合气体压力 435 psi（1 psi）下，其 CO 渗透性仍为 3324 Barrer，CO/CH 选择性为 14.7 = 6894.8 Pa)，优于2018年最新的CO/CH混合气体上限。结果表明，CO 渗透性提高了 100 倍，同时保持了 DBPO 的选择性，这归因于显着增强的超微孔性，增加了扩散和溶解度系数，同时保持了扩散和溶解度选择性。总之，脱溴与 TR 的结合为设计先进的 TR 膜提供了新的方向。