Polymers with efficient and tight chain-packing and thus strong size-sieving ability are of great interest for H₂/CO₂ separation. Herein, we demonstrate a new approach to manipulating polymer structure by acid doping, leading to superior H₂/CO₂ separation performance. We have doped polybenzimidazole (PBI) with polyprotic acids, specifically H₃PO₄ and H₂SO₄. These acids cross-link PBI chains and drastically decrease free volume, improving the material's H₂/CO₂ selectivity to far surpass the Robeson's 2008 upper bound for membrane performance. For example, PBI doped with H₃PO₄ at a molar ratio of 1 : 1 exhibits an unprecedented H₂/CO₂ selectivity of 140 at 150 °C, which exceeds that of previously known polymeric materials and is superior or comparable to that of state-of-the-art 2D materials with sharp size separation, such as graphene oxide, MoS₂, and metal–organic frameworks. This facile approach to enhancing polymer chain-packing efficiency opens up a new avenue for designing strong size-sieving polymers for membrane gas separations.

中文翻译：

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掺杂聚丙烯酸的聚苯并咪唑具有前所未有的筛分能力，可用于膜H ₂ / CO ₂分离†

对于H ₂ / CO ₂分离而言，具有高效且紧密的链堆积以及因此具有强大的筛分能力的聚合物引起了人们的极大兴趣。在本文中，我们展示了一种通过酸掺杂来操纵聚合物结构的新方法，从而实现了出色的H ₂ / CO ₂分离性能。我们已经用聚质子酸，特别是H ₃ PO ₄和H ₂ SO ₄掺杂了聚苯并咪唑（PBI）。这些酸交联了PBI链，并大大降低了自由体积，提高了材料的H ₂ / CO ₂选择性，远远超过了Robeson的2008年膜性能上限。例如，PBI掺杂了H摩尔比为1：1的₃ PO ₄在150°C下表现出前所未有的H ₂ / CO ₂选择性140具有清晰尺寸分离的2D材料，例如氧化石墨烯，MoS ₂和金属有机骨架。这种提高聚合物链堆积效率的简便方法为设计用于膜气体分离的强尺寸筛分聚合物开辟了一条新途径。