A method of making a porous membrane is disclosed. One such method optionally includes: forming a plurality of pillars in an array form over a substrate; and forming a layer with a mixture of a porous material precursor and a surfactant over the substrate. The method optionally includes removing the pillars to leave cavities in the layer; filling the cavities in the layer with a cavity filler; and removing the surfactant from the layer. The porous membrane can be used as, for example, a sieve for separating molecules from a chemical reaction.