Disclosed are a copolymer, porous membranes made from the copolymer, and a method of treating fluids to remove metal ions using the porous membranes, for example, from fluids originating in the microelectronics industry, wherein the copolymer includes monomeric units I and II, wherein monomeric unit I is of the formula A-X—CH2—B, wherein A is Rf—(CH2)n, Rf is a perfluoro alkyl group of the formula CF3—(CF2)x—, wherein x is 3-12, n is 1-6, X is O or S, and B is vinylphenyl, and monomeric unit II is vinylpyridine.