Pebax1657 is known as a promising polymeric membrane material for CO2 separation. In order to further improve its gas separation performance, different polymers containing ethylene oxide (EO) groups are incorporated into the Pebax1657 matrix to form mixed matrix membranes (MMMs). Liquid-like nanoparticle organic hybrid materials (NOHM-I-HPE, "I" stands for "ionic bond" and "HPE" refers to polyetheramine ("PE") with a high ("H") ether group content), which are made of polyetheramine chains tethered onto functionalized silica nanoparticles, have shown high solubility of CO2 . In this study, the homogenous NOHM-I-HPE/Pebax1657 MMMs with different NOHM-I-HPE loadings are prepared and investigated. The results indicate that the addition of NOHM-I-HPE leads to a decrease in glass transition temperature of Pebax1657 and an increase in EO content of the MMMs. Influences of NOHM-I-HPE content on CO2, N-2 and CH4 permeations are investigated at 23 degrees C and 1 bar. For the NOHM-I-HPE loading ranging from 0 to 60 wt%, solubility coefficients of the MMMs for CO2 greatly increase from 1.16 to 3.84 cm(3) (STP)/(cm(3) .bar), while those for CH4 and N-2 only increase from 0.078 to 0.094 cm(3) (STP)/(cm(3).bar) and from 0.013 to 0.026 cm(3) (STP)/(cm(3).bar), respectively. Although the CO2/N-2 selectivity slightly decreases with an increase in the NOHM-I-HPE loading, the CO2/CH4 selectivity is improved in the newly developed NOHM-I-HPE/Pebax1657 MMMs. These results indicate that the NOHM-I-HPE/Pebax1657 MMMs are very promising candidates for selective CO2 separation for various energy related applications.