methods have been developed to make porous ceramic membranes having macroscopic channels therethrough . the novel membranes are formed by temporarily supporting the sol - gel membrane precursor on an organic support which is ultimately removed from the interior of the membrane , preferably by pyrolysis or by chemical destruction . the organic support may also include an inorganic metal portion that remains on destruction of the organic portion , providing structural support and / or chemical reactivity to the membrane . the channels formed when the organic support is destroyed provide the ability to withdraw small catalytic products or size - separated molecules from the metal oxide membrane . in addition , the channel - containing membranes retain all of the advantages of existing porous ceramic membranes .