Zeolite-Encaged Pd–Mn Nanocatalysts for CO2 Hydrogenation and Formic Acid Dehydrogenation

A CO ₂ -mediated hydrogen storage energy cycle is a promising way to implement a hydrogen economy, but the exploration of efficient catalysts to achieve this process remains challenging. Herein, sub-nanometer Pd–Mn clusters were encaged within silicalite-1 (S-1) zeolites by a ligand-protected method under direct hydrothermal conditions. The obtained zeolite-encaged metallic nanocatalysts exhibited extraordinary catalytic activity and durability in both CO ₂ hydrogenation into formate and formic acid (FA) dehydrogenation back to CO ₂ and hydrogen. Thanks to the formation of ultrasmall metal clusters and the synergic effect of bimetallic components, the PdMn _0.6 @S-1 catalyst afforded a formate generation rate of 2151 mol _formate mol _Pd ⁻¹ h ⁻¹ at 353 K, and an initial turnover frequency of 6860 mol (Formula presented.) mol _Pd ⁻¹ h ⁻¹ for CO-free FA decomposition at 333 K without any additive. Both values represent the top levels among state-of-the-art heterogeneous catalysts under similar conditions. This work demonstrates that zeolite-encaged metallic catalysts hold great promise to realize CO ₂ -mediated hydrogen energy cycles in the future that feature fast charge and release kinetics.