Methods of fabricating a porous membrane are disclosed. The first method includes the following operations. A mesoporous silica thin film with perpendicular mesopore channels is grown on a polymer film. The mesoporous silica thin film and the polymer film are transferred onto a macroporous substrate, in which the polymer film is positioned between the macroporous substrate and the mesoporous silica thin film. The polymer film is removed to form the porous membrane. The second method includes the following operations. A polymer film is formed on a macroporous substrate, wherein the polymer film includes crosslinked polymers including cross-linked polystyrene, cross-linked polymethyl methacrylate, or a combination thereof. A mesoporous silica thin film with perpendicular mesopore channels is grown on the polymer film. The polymer film is removed to form the porous membrane.