Metal-organic framework (MOF) crystals of Cu-3(BTC)(2) with a high surface area (1396 m(2).g(-1)) were synthesized and mixed with polyimide (PI) to prepare mixed-matrix membranes (MMMs) for gas separations The PI-Cu-3(BTC)(2) blend was successfully spun into MMM hollow fiber by the dry/wet-spinning method SEM images of the fiber cross sections revealed significant plastic deformation of the polymer matrix owing to the strong affinity between Cu-3(BTC)(2) and PI The H-2 permcance and the selectivity of H-2 with respect to other gases such as N-2, CO2, O-2, and CH4 both Increased markedly with increased Cu-3(BTC)(2) loading At a loading of 6 wt % Cu-3(BTC)(2), the permeance of H-2 increased by 45%, and the ideal selectivity increased by a factor of 2-3 compared to the corresponding values for pure PI