A microporous metal-organic framework Cu-4,4'-bipyridine-hexafluorosilicate (Cu-BPY-HFS), having a surface area of 2000m(2)/g, was combined with Matrimid (R) polymer to form free standing films. The permeability properties of Cu-BPY-HFS-Matrimid (R) mixed-matrix membranes were tested for the pure gases H-2, N-2, O-2, CH4, and CO2 and the gas mixtures CO2/CH4, H-2/CO2 and CH4/N-2. The ideal selectivity of CH4/N-2 increased from 0.95 to 1.2 1, which suggests that Cu-BPY-HFS has a strong affinity towards CH4 and favors its permeation. The higher solubility of CH4 in the membranes leads to higher selectivity for CH4/N-2. The enhanced CH4 transport is also apparent in the case of ideal selectivity for CO2/CH4 and H-2/CH4. For CH4/N-2 gas mixtures, the selectivity increased from 0.95 to 1.7. The Cu-BPY-HFS's affinity towards CH4, and its large surface area increased the solubility of CH4 in the mixed-matrix membranes, which led to higher selectivity towards CH4. (C) 2008 Elsevier B.V All rights reserved.