An inorganic/organic micro-double-network (mu-DN) ion gel-based composite membrane with good mechanical properties and high CO2 permeance was developed in this study. The mu-DN ion gel was composed of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C(4)mim][Tf2N]), a cross-linked polymer network, and silica nanoparticle clusters. The mechanical strength of the mu-DN ion gel was optimized to achieve a fracture energy of 636 kJ/m(3). The fabricated composite membrane with an ion gel layer thickness of 4.5 mu m shows a CO2/N-2 permselectivity of 23 and a CO2 permeance of 119 GPU. The gas permeance of the composite membranes was calculated by considering a series of diffusion processes, and the results were in good agreement with the experimental data. The calculation results obtained using the proposed model show high potential of our mu-DN ion gel to achieve much higher CO2 permeance.