Aromatic Polyimine-Derived Carbon Membranes for Efficient Hydrogen Separation

Hydrogen is a key energy carrier for the transition toward sustainable energy systems, yet its widespread implementation relies on efficient and selective purification from mixed gas streams. Carbon membranes have emerged as promising candidates for hydrogen separation due to their scalable fabrication, excellent thermal and chemical stability, and tunable pore structures, including micropores (d_p ≤ 2 nm) and ultra-micropores (d_p ≤ 0.7 nm). In this work, an aromatic polyimine precursor incorporating kinked structural motifs is synthesized via a facile, catalyst-free route to introduce intrinsic free volume and high carbon yield upon pyrolysis. Two distinct carbonization protocols are employed to investigate relationship between pyrolysis conditions, carbon structure, and membrane performance. The resulting carbon membranes exhibit high hydrogen permeance up to 3.61 × 10^-7 mol m^-2 s^-1 Pa^- 1 (200°C) and exceptional selectivities of 214 (H₂/N₂) and 759 (H₂/CH₄) at 20°C. A correlation between pore size distribution and separation performance is established, demonstrating that controlled pyrolysis enables tuning of the micropore to ultra-micropore ratio. As a result, the membranes surpass the Robeson upper bound, and compare favorably to several state-of-the-art membrane materials, including CMs derived from other polymeric precursors, highlighting their strong potential for high-performance hydrogen separation.