Unambiguous evidence supporting the decomposition reaction of NO on two types of monovalent copper-ion in CuZSM-5 zeolite

By combining the methods of calorimetry and spectroscopy using CO as a probe molecule, we obtained the evidence supporting the decomposition reaction of NO on two types of monovalent copper-ion (Cu⁺) species in CuZSM-5 zeolite. These Cu⁺ species showed the characteristic emission bands at 21,000 and 18,500 cm^-1 and, respectively, gave the CO adsorption heats of 122 and 110 kJ mol^-1. Taking account of our previous EXAFS data, it was found that the former species take the two-coordinated structure involving lattice oxygen atoms, while the latter ones the three-coordinated structure. In this paper, we also emphasized the validity of our original assignment of active sites on CuZSM-5 for N₂ adsorption at room temperature; three-coordinated Cu⁺ species adsorb N₂ molecules.