Mordenites with SiO₂/Al₂O₃ molar ratio (MR) of 13, 20 and 90 were exchanged with a Ni²⁺. The samples were characterized by XRD, EDS, DRS and TEM. UV-Vis spectra of all Ni-exchanged samples were typical for a Ni(H₂O)₆²⁺ ions octahedrally coordinated by water molecules. In the UV range, samples with MR of 20 and 90 showed absorption around 250-300 nm due to partial dehydration on Ni²⁺ ions and their coordination with O^2- of the zeolite framework. It was revealed that Ni species formed on mordenite NiNaMor13 with low molar ratio are weakly bound to the mordenite framework; as a consequence, high catalytic activity in NO reduction is observed. Easy red-ox transformation of such a species results in the activation of propene pyrolysis with formation of carbon nanostructures.