A method is provided for producing a permeable membrane, comprising the steps of aligning a plurality of hollow nanotubules to form a mat, coating the mat with a continuous polymer matrix to form a membrane. The membrane is etched (a) to open the plurality of hollow nanotubules and form pores and (b) to oxidize the carboxyl groups to carboxylate groups. At least one additional functional unit having at least one available amine group to bind the at least one additional functional unit to the nanotubule end carboxylate group may be provided. Membranes fabricated in accordance with the method of the invention are provided also.