Thermoresponsive poly(N-isopropylacrylamide) with triazole copolymer brushes, poly(NIPAAm-co-TZ), grafted on porous silica (P-SiO2) was synthesized, and the temperature swing-based mutual separation of trivalent lanthanide ions (Ln(3+)) was demonstrated. The results indicated that the polymer brushes enabled adsorption/desorption of Ln(3+) depending on differences in the interactions between the individual Ln(3+) and TZ moieties, and the hydration state.