Mixed matrix membranes are prepared from zeolites and polymers, such as polyimides, in a void free fashion where either no voids or voids of less than several Angstroms are present at the interface of the polymer and the zeolite by bonding (hydrogen, ionic, or covalent) functional groups on the zeolite with functional groups on the polymer. The mixed matrix membranes may be cast or formed by ISAM processes, and may be present on a variety of supports including hollow fibers.