An electrolyte membrane for an energy storage device, the membrane including a matrix including a first ionically conductive polymer; an alkali metal salt, an alkaline earth metal salt, or a combination thereof; a metal-organic framework; and a second ionically conductive polymer miscible with the first ionically conductive polymer, wherein the second ionically conductive polymer is covalently bound to a portion of or the entire surface of the metal-organic framework through at least one amide bond.