A novel approach to improve the selectivity of mixed matrix membrane (MMM) systems was developed. MOF nanoparticles (NPs) were chemical coated by a PEG based shell and then incorporated into a polymer matrix to yield a MMM. The unique design of the core-shell MOF NPs can enhance both the membrane permeability and selectivity simultaneously. This membrane material exhibits excellent CO2/N-2 separation performance that surpasses the latest upper bound through the most direct way. This filler was also applied to the thin-film composite membrane system, showing promising performance and placing it in the optimal zone for postcombustion CO2 capture.