Coaxial 3D Printing Enabling Mn/CHA@Pd/CHA Zeolite‐Based Core–Shell Monoliths for Efficient Passive NOx Adsorbers

Abstract Pd‐based zeolites are extensively used as passive NO x adsorbers (PNA) for cold‐start NO x emissions to meet stringent emission regulations. However, optimizing adsorber design to reduce Pd usage with substitution by non‐noble metals that are prone to suffer from H 2 O remains a significant challenge. Herein, the core–shell Mn/CHA@Pd/CHA zeolite monoliths based on non‐noble metal/zeolite core are constructed using coaxial 3D printing technology and identified as efficient passive NO x adsorbers for the first time. In the Mn/CHA@Pd/CHA monolith, the Pd/CHA shell effectively protected the Mn active sites in the core from H 2 O, while the integration of the Mn/CHA core not only introduced efficient storage sites but also facilitated NO x desorption, thereby achieving comparable adsorption properties and increased the NO x desorption efficiency by 35% at 350 °C compared with that of Pd/CHA monolith. Furthermore, some non‐noble metal‐based zeolites (e.g., Co/CHA, Mn/MFI, Mn/BEA) and Pd‐based zeolites (e.g., Pd/AEI) are also employed as cores and shells respectively to fabricate a series of core–shell zeolite monoliths via coaxial 3D printing, highlighting the benefits of incorporating non‐noble metals into Pd‐based zeolites for improving adsorption and desorption behaviors. This work provides a promising strategy for designing cost‐effective PNA materials and contributes to improving the exhaust after‐treatment technology.