Removal of magnesium and calcium cations in water, called water softening, is an important procedure for industrial use. Although ion exchange resin and chelate resin are one of the most widely used materials for desalination, they have a drawback in regeneration, in which huge amount of salt or strong acidic/basic aqueous solution needs to be applied. In this research, sulfonamide-derived cation capturing system was suggested as an alternative. Sulfonamide derivatives usually show a sharp transition from charged to uncharged form at a specific pH, which alleviates the condition of regeneration. A variety of sulfonamide derivatives were introduced to polystyrene microbeads. 1.88±0.05 mmol/g of the sulfonamide-based ligand was introduced in maximal amount Cation chelating capacities of products were quantified through calcium ion capturing test, identifying several sulfonamides as promising cation capturing systems. Finally, their metal ion capturing capacities within specific pH ranges and regeneration properties in moderate acidic condition were verified. Among the surface-treated sulfonamide derivatives, glycine-conju-gated sulfonamide group, which had 0.90±0.01 mmol/g of ion capturing capacity and rapidly regenerated at pH 5.0, was found to be most appropriate for water softening application.