A penta-aza ligand was designed using the Density Functional Theory (DFT), synthesized, and then loaded on a polystyrene matrix to prepare a functional polymer as a Co(II) selective adsorbent. A comparative experimental study on adsorption of Co(II) and Zr(IV) revealed that the polymer-supported ligand is more selective toward Co (II) than Zr(IV) from aqueous acidic solutions. The maximum adsorption capacities of the adsorbent for Co(II) and Zr(IV) were 4.1 and 0.5 mg/g, respectively, at pH 1.0. Vibrational frequencies of the metal ligand complexes were calculated with the VWN-BP functional to confirm true local minima.