Abstract High-performance membrane materials are urgently demanded for efficient membrane-based biogas upgrading. Polyelectrolytes with convertible ionic groups, spontaneously forming interconnected facilitated transport pathways for gas molecules via microphase separation, exhibit promising potential in membrane-based separation. However, there is a great challenge to further enhance the gas permeability and selectivity simultaneously due to the limited microphase separation and low free volume generated by the strong interaction between ionic groups. Herein, we demonstrate a novel strategy to construct the tunable hollow quaternary ammonium (-N+(CH2CH3)3) clusters with good CO2 affinity via sacrificial template method in quaternized polysulfone (QAPSf) membranes for achieving the fast transport of CO2. The templates (POSS) induce the formation of –N+(CH2CH3)3 clusters through forced microphase separation in the membranes and then are etched away to generate hollow CO2-philic clusters to increase the fractional free volume in membranes and thus improve CO2 diffusion. After that, the B(OH)4- as counterions by ion exchange endow the hollow CO2-philic clusters with high CO2-facilitating ability, which simultaneously enhance the CO2 permeability and CO2/CH4 selectivity. The resultant QAPSf-B(POSS-2) membrane exhibits superior separation performance with an optimal permeability of 1113 Barrer and a CO2/CH4 gas selectivity of ~45, i.e. 334% and 73% higher than the pristine QAPSf membrane, respectively, breaking the trade-off between permeability and selectivity and surpassing the Robeson 2008 upper-bound.

中文翻译：

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具有可调中空亲二氧化碳团簇的聚电解质膜通过牺牲模板用于沼气升级

摘要 高效的膜基沼气升级迫切需要高性能的膜材料。具有可转换离子基团的聚电解质通过微相分离自发形成气体分子的互连促进传输途径，在基于膜的分离中表现出良好的潜力。然而，由于离子基团之间的强相互作用产生的微相分离有限和低自由体积，进一步提高气体渗透性和选择性是一个巨大的挑战。在此，我们展示了一种新策略，通过在季铵化聚砜 (QAPSf) 膜中通过牺牲模板方法构建具有良好 CO2 亲和力的可调中空季铵 (-N+(CH2CH3)3) 簇，以实现 CO2 的快速传输。模板 (POSS) 通过膜中的强制微相分离诱导 –N+(CH2CH3)3 簇的形成，然后被蚀刻掉以生成中空的亲 CO2 簇以增加膜中的部分自由体积，从而改善 CO2 扩散。之后，B(OH)4-作为抗衡离子通过离子交换赋予中空亲CO2簇具有高CO2促进能力，同时提高了CO2渗透性和CO2/CH4选择性。所得的 QAPSf-B(POSS-2) 膜表现出优异的分离性能，最佳渗透率为 1113 Barrer，CO2/CH4 气体选择性为~45，即分别比原始 QAPSf 膜高 334% 和 73%，打破了渗透率和选择性之间的权衡并超过 Robeson 2008 上限。