A cross-linked polyimide is disclosed. The cross-linked polyimide includes a polyimide and at least one oxygenated hydrocarbon. The oxygenated hydrocarbon cross-links the polyimide. A porous cross-linked membrane is also disclosed. The porous cross-linked membrane includes a support structure and a cross-linked polyimide disposed on the support structure. The cross-linked polyimide includes a polyimide; and at least one oxygenated hydrocarbon cross-linking the polyimide. Also disclosed are methods of making the cross-linked polyimide and the porous cross-linked membrane.