Silica Nanohybrid Membranes with High CO₂ Affinity for Green Hydrogen Purification

An effective separation of CO 2 from H 2 can be achieved using currently known polyethylene oxide (PEO)‐based membranes at low temperatures but the CO 2 permeability is inadequate for commerical operations. For commercial‐scale CO 2 /H 2 separation, CO 2 permeability of these membranes must be significantly enhanced without compromising CO 2 /H 2 selectivity. We report here exceptional CO 2 /H 2 separation properties of a nanohybrid membrane comprising polyethylene glycol methacrylate (PEGMA) grafts on an organic‐inorganic membrane (OIM) consisting of a low molecular weight polypropylene oxide (PPO)‐PEO‐PPO diamine and 3‐glycidyloxypropyltrimethoxysilane (GOTMS), an alkoxysilane. The CO 2 gas permeability of this nanohybrid membrane can reach 1990 Barrer with a CO 2 /H 2 selectivity of 11 at 35 °C for a mixed gas mixture comprising 50% CO 2 ‐ 50% H 2 at 3.5 atm. The transformation of the inorganic silica phase from a well‐dispersed network of finely defined nanoparticles to rough porous clusters appears to be responsible for this OIM membrane exceeding the performance of other state‐of‐the‐art PEO‐based membranes.