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

Developing highly efficient, stable, and wide-temperature NH3-SCR catalysts is one of the major challenges in industrial NOx 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 (deNOx) 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 CeSnOx/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% NOx conversion and ~100% N2 selectivity over a temperature window exceeding 300 °C. This work highlights zeolite-mediated NH3 storage in deNOx, providing mechanistic insight into OXZEO structure-property relationships and guiding the development of next-generation NH3-SCR catalysts. Controlling nitrogen oxide emissions needs catalysts that work across harsh conditions. This study separates ammonia storage from reaction sites in oxide-zeolite hybrids, enabling stable, selective removal over a wide temperature range.