a multilayer membrane for performing reverse osmosis is disclosed . the membrane comprises a porous support and interfacially polymerized thereon a superposed layer of poly meta - phenylene tetrahydrofuran - 2 , 3 , 4 , 5 - tetracarboxamide in which up to 50 mole % of the tetrahydrofuran - 2 , 3 , 4 , 5 - tetracarboxamide units have been replaced with isophthalamide or terephthalamide units . the preferred material for forming the support is a polysulfone .