An effective separation of CO2 from H2 can be achieved using currently known polyethylene oxide (PEO)-based membranes at low temperatures but the CO2 permeability is inadequate for commerical operations. For commercial-scale CO2/H2 separation, CO2 permeability of these membranes must be significantly enhanced without compromising CO2/H2 selectivity. We report here exceptional CO2/H2 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 CO2 gas permeability of this nanohybrid membrane can reach 1990 Barrer with a CO2/H2 selectivity of 11 at 35 °C for a mixed gas mixture comprising 50% CO2 - 50% H2 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.