Defect-rich amorphous structures with Sm-O-Mn electronic modulation enable efficient and poisoning-resistant low-temperature NH3-SCR

Mn-based catalysts are promising for low-temperature NH 3 -SCR, but their practical application is limited by insufficient N 2 selectivity and poor H 2 O/SO 2 tolerance. Herein, Sm-incorporated amorphous manganese oxide catalysts (SmMn x O y -AM) were designed to regulate the electronic structure of Mn active sites through local Sm-O-Mn interactions. The optimized SmMn 4 O y -AM catalyst achieved over 95% NO x conversion between 100 and 220 °C while maintaining N 2 selectivity above 80%. Notably, it maintained high NO x conversion during long-term stability and stepwise H 2 O/SO 2 tolerance tests at 120 °C, while the Sm-free Mn oxide (Sm 0 Mn 4 O y ) showed rapid SO 2 -induced deactivation. Experimental characterizations and DFT calculations revealed that Sm incorporation modified the local structure and electronic environment of Mn sites, facilitating NH 3 /NO adsorption and activation while suppressing excessive NH 3 oxidation. The combined results suggest that the proposed Sm–O–Mn interactions may contribute to changes in the Mn electronic environment, weaker SO 2 adsorption, and reduced sulfate accumulation. This work provides a feasible strategy for designing amorphous Mn-based catalysts with high activity, improved selectivity, and enhanced poisoning resistance for low-temperature NH 3 -SCR.