Fundamental insight into copper-based zeolite catalysts for NH3-SCR: Two decades’ progress and future perspectives

Abstract

Amidst tightening mobile-source emission regulations, ammonia selective catalytic reduction remains the dominant post-treatment technology for NO x removal, with copper-exchanged zeolites (Cu-zeolites) serving as benchmark catalysts. Here, we systematically survey zeolite topologies—such as MFI, CHA, AEI, and LTA—evaluating their catalytic performance, reaction mechanisms, hydrothermal stability, and resistance to poisoning. A comprehensive overall pathway of sequential two-NO activation on dual ZCuOH sites is unified and complements the established L-NH 3 (NH 3 bond to solvated Cu 2+ ions) activation model in the Reduction Half-Cycle. This work provides fundamental insights into the performance, hydrothermal stability, and SO 2 resistance of Cu-based zeolites. Therefore, the fundamentals and new mechanistic insights of hydrothermal aging are summarized over Cu-SSZ-13, while highlighting Cu-SSZ-39 as an intrinsically robust successor. We dissect the SO 2 poisoning mechanisms of Cu-CHA, demonstrating that engineering the atomic-scale distribution of Cu enhances both sulfur tolerance and hydrothermal stability. Supplementary strategies ( e.g ., constructing protective/sacrificial sites, co-crystallization, and core-shell structures) are also considered beneficial. Beyond durability, we also focus on the two-dimensional PST-9 zeolite and OFF/ERI intergrowths zeolite for the future challenge of diffusion. Finally, we outline future research frontiers, aiming to unify Cu-zeolite theory into a mechanistic framework that translates fundamental insights into rational design principles for next-generation catalysts.