Catalytic arene-norbornene annulation (CANAL) ladder polymer derived carbon membranes with unparalleled hydrogen/carbon dioxide size-sieving capability

Hydrogen is an emerging energy source with a wide range of applications in transportation, electricity generation, and manufacturing of important chemicals such as ammonia and methanol. Hydrogen is commonly coproduced with CO2 using steam reforming of methane and its purification is typically achieved using energy-intensive processes such as pressure swing adsorption (PSA) and cryogenic distillation. Membrane technology with potentially lower energy consumption and lower carbon footprint could play an important role in developing a more sustainable hydrogen economy. In this study, we prepared carbon molecular sieve (CMS) membranes by the pyrolysis of a highly aromatic catalytic arene-norbornene annulation (CANAL)-Tröger's base ladder polymer of intrinsic microporosity precursor — CANAL-TB-1. CMS membranes obtained by pyrolysis between 600 and 900 °C displayed excellent gas separation performance for hydrogen/carbon dioxide separation and related applications. The CANAL-CMS-800 °C membrane showed a pure-gas hydrogen permeability of 41 Barrer with H2/CO2, H2/N2, and H2/CH4 selectivity values of 39, 1952, and >8200 at 35 °C. Increasing the pyrolysis temperature to 850 and 900 °C further boosted the selectivity. For example, the CANAL-CMS-900 °C exhibited a stable long-term mixed-gas performance over a period of 38 days with an unprecedented H2/CO2 selectivity of 174 and H2 permeability of 8.2 Barrer at 10 bar total feed pressure and 100 °C, which significantly exceeded the performance of previously reported polymers and related CMS membrane materials.