Stabilizing Pd Catalysts for Liquid-Phase Hydrogenation of N-Heterocyclic Hydrogen Carriers through Zeolite Encapsulation

N-Heterocyclic aromatics can reversibly store H₂ through (de)-hydrogenation over supported Pd catalysts, but metal nanoparticles often sinter during liquid-phase reactions. Here, we report that the encapsulation of Pd nanoparticles in large-pore zeolites stabilizes Pd catalysts during hydrogenation of <i>N</i>-methylindole (N-MID). Flow reactor studies combined with post-reaction characterizations show that Pd nanoparticles supported on SiO₂ or Al₂O₃ sinter during hydrogenation of N-MID, while Pd/zeolites (particularly Pd/Beta) retain <2 nm particles, likely by suppressing the chelation and migration of Pd by N-MID. This work highlights the potential of zeolitic voids to suppress metal catalyst deactivation in liquid-phase reactions including H₂ storage in chemical bonds.