Zirconium–carboxylic ligand-based porous materials modified with –NH 2 groups originated either from melamine or urea were synthesized. The samples were used as adsorbents of NO 2 from either dry or moist air. The surface features were analyzed using SEM, XRD, nitrogen sorption, thermal analysis and FT-IR. The incorporation of urea, which is a planar molecule, results in a highly porous crystalline materials. Melamine, a triazine compound, on the other hand obstructs the nucleation and growth of the crystals due to its interaction with metallic centers and carboxylic ligands and leads to amorphous materials with low porosity. Water enhances the NO 2 adsorption process. Introducing Lewis basic sites by the incorporation of –NH 2 groups promotes chemical reactions on the surface. The amine (NH 2 ) or the carbonyl (CO) groups in urea directly interact with NO 2 molecules in both moist and dry conditions, which leads to the formation of surface bound nitrates. In the case of melamine modified materials the hydrolysis of the terminal secondary –NH 2 creates oxygen rich functional groups that cause the formation of surface bound nitrate species.