Enhanced intrinsic water and sulfur dioxide tolerance of Cu-SSZ-13 for NH₃-SCR via surface Al siting and micropore confinement

Low-temperature nitrogen oxides (NO_x) abatement is critically hindered by catalyst deactivation in H₂O- and SO₂-containing atmospheres, severely limiting the practical application of NH₃-selective catalytic reduction (NH₃-SCR) technology. Existing strategies to improve the tolerance of Cu-based chabazite (Cu- CHA ) catalysts primarily rely on external modifications, overlooking the intrinsic molecular sieving potential of their micropore structure. Herein, we propose a strategy to intrinsically enhance the water and sulfur dioxide tolerance of Cu- CHA catalyst by regulating the surface framework Al distribution and synergistically amplifying the micropore confinement effect. Therefore, a Cu-SSZ-13-M with an Al-poor surface was synthesized, which effectively reduces the number of surface-exposed active Cu species and acid sites while enhancing surface hydrophobicity, thereby suppressing NH₄HSO₄ formation and mitigating pore-mouth blockage. Meanwhile, the unblocked micropore channels act as a molecular-scale diffusion barrier, selectively restricting SO₂ ingress and protecting intracrystalline active sites from poisoning. In the NH₃-SCR reaction over 22 h in the presence of H₂O and SO₂, Cu-SSZ-13-M exhibits a 32% higher NO_x conversion than Cu-SSZ-13-C. By integrating surface active site regulation with pore-level mass transport control, this work unveils the microscopic mechanism underlying the enhancement of intrinsic tolerance of Cu- CHA catalysts and offers a rational design strategy for highly efficient and anti-poisoning NH₃-SCR catalysts.