2) It is produced by steam reforming of fossil fuel followed by high-temperature and low-temperature water-gas shift (WGS) reaction. Syngas containing a mixture of hydrogen and carbon dioxide (CO2) is then separated into a high-purity H2 stream. This separation is currently achieved at a large scale by contacting H2/CO2 mixture in a solvent where CO2 is selectively absorbed. Processes that can improve the energy efficiency of hydrogen purification and reduce the associated carbon capture penalty as well as related environmental emissions have been intensively investigated. Membrane-based separation is highly promising in this context because it is environment-friendly, and does not rely on thermal energy but on partial pressure difference of H2 across the membrane. High-temperature separation of H2/CO2 mixture also allows integration of the WGS reaction with separation improving the overall process efficiency. Membrane-based H2 separation relies on a selective transport pathway for H2. Dense palladium membranes yield high H2 permeance (flux normalized by transmembrane pressure difference (∆𝑃)) as well as a high selectivity via chemisorption and diffusion of H in interstitial lattice site , however, they face challenges from a high material cost and instability in the presence of hydrocarbon, CO, and H2S . Separation using polymeric membranes benefits from the high processibility of polymers . However, the state-of-the-art polybenzimidazole-based membranes yield modest H2 permeance and H2/CO2 selectivity. This is mainly because the kinetic diameters of H2 and CO2