In this study, a 'green" method has been discovered by utilizing the amino functional poly(ethylene oxide) (PEO) and epoxy functional PEO with low molecular weights to synthesis cross-linked membranes for enhancing H-2 purification and CO2 capture performance by retarding the crystallinity of semi-crystalline polymer of PEO. The cross-linking reaction can happen simply by mixing two materials without using any solvent. The reaction has been characterized by Fourier transform infrared-attenuated total reflectance (FTIR-ATR), X-ray photoelectron spectroscopy (XPS), solid-state C-13 nuclear magnetic resonance (NMR) and the gel content test. Furthermore, X-ray diffraction (XRD) and differential scanning calorimeter (DSC) confirm the amorphous structure of cross-linked PEO membranes, which should benefit the gas transport. The gas transport properties and the plasticizing phenomenon of CO2 have been examined in detail. Interestingly, the investigation on CO2 plasticization phenomenon reveals that the cross-linked PEO membrane should be plasticized immediately after the pressure load. The pressure dependence of CO2 permeability in the pressure range from 0.25 atm to 30 atm can be separated into two stages based on the permeability increment although the CO2 permeability continuously increases with the loading pressure. The gas transport results illustrate that CO2 has much larger permeability than that of any tested gas (including H-2, N-2 and CH4) attributing to the CO2-philic characteristic of ethylene oxide (EO) groups in the cross-linked PEO membrane. The good permeability and selectivity make the developed PEO membrane promising for H-2 purification and CO2 capture applications. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.