Sn-Mediated Regulation of the O ₂ Adsorption and Activation Capacity of the Ir/SAPO-34 Catalyst: A Key to Boosting CO Selective Catalytic Reduction of NO x in O ₂ -Enriched Environments

Selective catalytic reduction (SCR) of NOx by CO has emerged as a highly promising approach for industrial sintering flue gas control, effectively eliminating the requirement for external reductants such as NH₃. However, conventional SCR catalysts suffer from limited operational temperature windows, primarily due to the preferential oxidation of CO through the O₂ activation pathways rather than participating in NOx reduction cycles, leading to significantly narrowed effective reaction zones. Herein, we proposed a Sn-doped strategy to mitigate O₂ activation on the Ir/SAPO-34 zeolite catalyst by structural tailoring of metal-oxygen bonds. The T₈₀ window (NOx conversion >80%) was remarkably expanded from an isolated active point to a 50 °C span. Furthermore, IrSn/SAPO-34 shows robust stability in the coexistence of SO₂ and H₂O, demonstrating unprecedented adaptability in practical exhaust treatment scenarios. Sn modification strengthens Ir-Sn covalent interactions, increasing d-band holes that suppress O₂ adsorption/dissociation. This slows CO oxidation via O₂, enhancing CO utilization for NOx reduction. Ir/SAPO-34 shows higher low-temperature NOx conversion due to superior CO oxidation activity, and IrSn/SAPO-34 demonstrates superior high-temperature performance through optimized reaction pathways. This study advances the design of high-efficiency Ir-based catalysts for CO-SCR reactions under practical flue gas treatment through an innovative strategy.