Recent advances in H2 purification and CO2 capture: Evolving from flat sheet to hollow fiber membranes

Hydrogen (H₂) production and demand have steadily increased, leading to a rise in carbon dioxide (CO₂) emissions since fossil fuels are the current raw material for H₂ production. Thin film composite (TFC) hollow fiber membranes have become significant in H₂ purification and CO₂ capture, playing a critical role in developing next-generation fuels and supporting the United Nations Sustainable Development Goal 7 (SDG 7) – Affordable and Clean Energy, with the goal of providing universal access to clean, advanced, and renewable energy for all. However, the polymeric selective layer of TFC membranes faces a trade-off between permeability and selectivity, as well as challenges including CO₂ plasticization and physical aging. Additionally, H₂/CO₂ separation remains particularly challenging because H₂, being diffusivity-selective, permeates more quickly through the membrane due to its smaller molecular size and higher kinetic energy, while CO₂, being solubility-selective, has a high affinity for dissolving in most polymeric membranes. Herein, this review provides an in-depth exploration of innovative modification strategies designed to overcome these challenges in glassy polymeric membranes and enhance H₂ separation performance in the recent 10 years. Various nanofillers, such as metal-organic frameworks (MOFs) such as University of Oslo (UiO), Materials Institute Lavoisier (MILs), and Zeolitic Imidazolate Frameworks (ZIFs), have shown remarkable potential in boosting gas separation capabilities due to their superior compatibility with polymer matrices and tunable properties. The review also explores different types of hollow fiber membranes, including single layer, dual-layer, and TFC, alongside fabrication techniques like interfacial polymerization and dip-coating. Critically, the analysis highlights cutting-edge strategies to improve membrane performance, such as (i) thermal cross-linking, (ii) chemical cross-linking, (iii) ultraviolet (UV) cross-linking, (iv) polymer blends, and (v) modified fillers, along with their objectives and expected outcome. Furthermore, the review spotlights breakthroughs in H₂/CO₂, H₂/CH₄, and H₂/N₂ separation technologies, emphasizing the critical need for continued innovation to drive sustainable H₂ production and meet the growing clean energy demand.