Self-supporting polymer thin films were obtained by the polymerization of an AB3-type hydrogen-bonded complex in the plastic columnar phase. Porous polymers with pore diameters of ≈1.1 and ≈1.6 nm lined with either -COOH or -COONa groups were fabricated from the polymer thin films. Both the pore size and pore collapse influence the adsorption of cations.