Functionalized membranes for use in applications, such as electrodeionization, can be prepared simply and efficiently by coating a conductive carbon nanotube and polymer membrane with a metal layer; and contacting the coated membrane with a solution comprises at least one electrochemically active and functional compound under conditions suitable for electrochemically depositing the electrochemically active and function compound on a surface of the metal-coated membrane. Such membranes may be reversible modified by chemically or electrochemically oxidizing the metal layer from the polymer membrane surface, thereby, providing a fresh surface which may be re-modified according to the preceding methods.