Open AccessMn-Doped Maghemite (γ-Fe2O3) from Metal–Organic Framework Accompanying Redox Reaction in a Bimetallic System: The Structural Phase Transitions and Catalytic Activity toward NOx Removal
Author(s) -
Jun Hyung Lee,
SeungYeop Kwak
Publication year - 2018
Publication title -
acs omega
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.779
H-Index - 40
ISSN - 2470-1343
DOI - 10.1021/acsomega.7b01865
Subject(s) - maghemite , bimetallic strip , superparamagnetism , calcination , materials science , redox , x ray photoelectron spectroscopy , catalysis , inorganic chemistry , thermal decomposition , phase (matter) , metal , oxidizing agent , metal ions in aqueous solution , chemistry , magnetite , chemical engineering , magnetization , metallurgy , biochemistry , physics , organic chemistry , quantum mechanics , magnetic field , engineering
Mn-doped maghemite (γ-Fe 2 O 3 ) particles were generated from a binary metal (Fe,Mn)-based metal-organic framework (MOF) via thermal decomposition under air. The X-ray photoelectron spectroscopy analysis revealed that the synthesis of Fe/Mn-MOF accompanied the reduction of the metal ions. The existence of Mn ions in this synthetic process leads to thermally stable maghemite particles under air. A temperature-induced structural phase transition from γ-Fe 2 O 3 to α-Fe 2 O 3 was observed through a mixed phase with another structure. Mn-doped γ-Fe 2 O 3 and α-Fe 2 O 3 exhibit superparamagnetic behavior. The sample annealed at 600 °C showed a mixed magnetic hysteresis loop indicating the existence of an intermediate structural phase between γ-Fe 2 O 3 and α-Fe 2 O 3 during the phase conversion from FeMn-MOF. The constructed Mn-doped iron oxides are active toward reducing nitric oxide with NH 3 . The NO conversion is 97% over Mn-doped γ-Fe 2 O 3 calcined at 320 °C.