Formation of reactive oxygen by N2O decomposition over binuclear cationic sites of Fe-ferrierite zeolite: Periodic DFT + U study

Highlights: • N₂O decomposition over [Fe²⁺Fe²⁺] doped Fe-FER was studied by periodic DFT + U. • N₂O decomposition over binuclear [Fe²⁺Fe²⁺] units occurs in a single step. • Calculated activation energy of N₂O decomposition is 8.6 kcal/mol. • N₂O decomposition yields a reactive oxygen atom bound to one iron atom FeO. The electronic nature of sites over Fe-ferrierite zeolite stabilizing active α-oxygen is analyzed by the periodic DFT + U approach. It is shown that two antiferromagnetically coupled Fe²⁺ cations with bridging OH-bonds form a stable bi-nuclear site of the [Fe²⁺Fe²⁺] doped FER complex. Frontier orbitals of this complex populated by two electrons with minority spins are localized in the bandgap. As a result, [Fe²⁺Fe²⁺] unit acquires the properties of a binuclear Lewis acid dipolarophile for 1,3-dipole N₂O. First reaction step of N₂O decomposition follows the Huisgen′s concept of the 1,3-dipolar cycloaddition concept followed by the formation of reactive oxygen species FeO.