The present invention discloses a new class of high flux mixed matrix membranes that are made by incorporating porous inorganic fillers (e.g. microporous and mesoporous molecular sieves, carbon molecular sieves, porous metal-organic frameworks) into a high flux high surface area microporous organic polymer matrix. These microporous organic polymers are referred to as “polymers of intrinsic microporosity” or PIMs. The high flux membranes are promising for a wide range of separations including liquid separations such as pervaporation of phenol/water and also gas separations in the petrochemical, refinery, and natural gas industries such as methane/carbon dioxide, olefin/paraffin and iso/normal paraffins separations.