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.