Pore Engineering of Carbon Molecular Sieve Membranes via Confined Ionic Liquids for Simultaneous Enhancement of Gas Permeability and Selectivity

Efforts for the enhancement of membranes for efficient gas separation are crucial to address challenges in carbon capture and hydrogen economy applications. A novel pore engineering strategy for CMS membranes via ionic liquids (ILs) is presented in this work. Analysis revealed that [Emim][Tf2N] functioned as a porogen and a structural modulator during carbonization, creating interconnected pore channels that facilitated efficient gas transport pathways while enabling appropriate d-spacing (3.55 Å) and precise pore formation (2.5–3.5 Å) for size-sieving of H2 (2.89 Å) and CO2 (3.3 Å). By optimizing the [Emim][Tf2N] loading and carbonization temperature, the optimal membrane with 3 wt % ILs under 550 °C (PI-3[Emim][Tf2N]-550) exhibited a simultaneous enhancement of both high permeability (H2 = 10883.1 Barrer; CO2 = 5697.6 Barrer) and selectivity (H2/N2 = 83.4, H2/CH4 = 113.7, CO2/N2 = 39.8, and CO2/CH4 = 45.5), surpassing the latest Robeson upper bound. Furthermore, the membrane exhibited superior antiplasticization properties and remained stable over 7 days, which was promising for practical H2 and CO2 separation applications.