Zeolitic isolated protonic acid sites-mediated NH₃ storage for robust NO_x removal.

Abstract

Developing highly efficient, stable, and wide-temperature NH₃-SCR catalysts is one of the major challenges in industrial NO_x emission control. Herein, we present an oxide-zeolite (OXZEO) hybrid design strategy for overcoming the challenge by spatially separating the NH₃ storage and redox functions via isolated zeolitic Brønsted (B) acid sites, in contrast to conventional regulation strategies that rely on Lewis acid sites. Through a combination of in situ spectroscopy, in situ mass spectrometry, ab initio molecular dynamics, and density functional theory, we identify a previously unrecognized denitrification (deNO_x) mechanism unique to the OXZEO system. Zeolitic B acid sites act as highly regulated NH₃ storage, and the stored NH₃ desorbs and migrates to oxide active sites as NH₃ and NH₄⁺, the latter effectively suppressing high-temperature NH₃ over-oxidation. Using CeSnO_x/Beta as the main model system for mechanistic investigation, we further demonstrate that this strategy can be generally extended to diverse zeolite topologies (BEA, CHA, MFI, FAU) and Ce-/Mn-based oxides, affording catalysts that achieve >80% NO_x conversion and ~100% N₂ selectivity over a temperature window exceeding 300 °C. This work highlights zeolite-mediated NH₃ storage in deNO_x, providing mechanistic insight into OXZEO structure-property relationships and guiding the development of next-generation NH₃-SCR catalysts.