Porous metal–organic framework MIL-100(Fe) as an efficient catalyst for the selective catalytic reduction of NOx with NH3

Abstract

The development of an efficient catalyst with excellent catalytic activity and high SO₂ resistance at low temperatures (<300 °C) remains a challenge for the selective catalytic reduction (SCR) reaction. In this study, we report that MIL-100(Fe) is an alternative catalyst for the SCR of NO_x with NH₃, and it exhibits higher NO_x conversion than the conventional V₂O₅–WO₃/TiO₂ catalyst below 300 °C. In addition, the effect of H₂O and SO₂ on the catalytic activity is reversible, and NO_x conversions are recovered after ceasing the flow of SO₂ and H₂O. In situ diffuse reflectance infrared Fourier transform spectroscopy results indicate that both ionic NH₄⁺ and coordinated NH₃ existed on MIL-100(Fe) and that the reaction primarily followed the Langmuir–Hinshelwood mechanism, in which NH₄⁺ reacts with NO₂ formed from NO oxidation over iron sites. Furthermore, the redox properties of the iron species (Fe³⁺ + e⁻ ↔ Fe²⁺) could play a significant role in activating the reactants.