• • The Mn7-Cu3-Nb0.05/BCN catalyst, with a Nb doping amount of 0.05%, achieves a NO conversion efficiency of ≥94% in the temperature window of 150–275 °C, demonstrating superior low-temperature activity for biomass flue gas denitration.
• • The catalyst exhibits dual E-R and L-H reaction pathways at low temperatures, with DFT calculations showing that the E-R pathway involves NH3 adsorption on the Mn-2 site (adsorption energy: −299.1 kJ/mol) and dehydrogenation with a low energy barrier of 15.5 kJ/mol, while the rate-determining step (NH2NO decomposition) has an energy barrier of 22.5 kJ/mol.
• • In the L-H pathway, NO is adsorbed on the Mn-1 site and oxidized to NO2 with a low energy barrier, rapidly forming bridged nitrate species that react with NH4+ to produce NH4NO3, which decomposes into N2 and H2O; no transition state is observed in key steps, confirming the rapid reaction characteristics.
• • The catalyst shows improved resistance to alkali metal K poisoning, a critical advantage for real-world biomass combustion flue gas containing potassium, thereby extending catalyst lifetime and reducing operational costs.