Membrane separations have been considered as an alternative to conventional separation techniques due to their low capital cost and high-energy efficiency. To further enhance the commercial applicability of membrane technology, mixed matrix membranes (MMM) were developed. The goal in developing the MMM is to enhance the membrane slectivity through gas solubility optimization. In this study, all MMM were prepared by a solution-casting method and then tested for CO2/N2 separation using a membrane testing unit at room tmperature. The liquid polyethylene glycol (PEG) emulsified silicone rubber MMM enhanced the selectivity of CO2/N2. However, the MMM possess limited stability resulting from the undesirable PEG leakage. To stabilize the MMM, activated carbon was incorporated into PEG. Apparently, the MMM composed of K2CO3 showed higher selectivity to CO2 since the carbonate ions could react reversibly with CO2 in the presence of water. Such ions could selectively carry CO2 across the membrane via the facilitated transport mechanism.