Design of a Stable PdH _0.706 Catalyst Supported on a Hydrophobic Aromatic Siloxane Framework for Hydrogenation Reactions

Palladium-based catalysts are widely used in hydrogenation reactions, but stabilizing the active species PdHx remains challenging. Meanwhile, catalysts capable of reducing nitro groups, aldehyde groups, alkenes, and azo groups typically lack selectivity when multiple functional groups coexist. Herein, sodium methylsilicate and pyromellitic dianhydride are employed as raw materials to synthesize a silicon-based porous material (Sips) for supporting PdH0.706 nanoparticles (PdH0.706 NPs) via H2O-assisted grinding. The specificity of the skeleton stabilizes the active center and promotes the hydrogenation performance. The porous 3PdH0.706Ac@Sips-L1-2 demonstrates outstanding hydrogenation activity, selectivity, recyclability, and substrate compatibility under room temperature and atmospheric H2 pressure. Specifically, nitrobenzene can be completely converted into aniline within 40 min, with a five-cycle efficiency of up to 93.51%. Additionally, the system efficiently reduces various substituted nitrobenzenes, demonstrating a strong substrate compatibility. It deserves mentioning that this system can also accomplish the hydrogenation of benzaldehyde to benzyl alcohol using water as the solvent. Importantly, even in the presence of both nitro and aldehyde functional groups, 3PdH0.706Ac@Sips-L1-2 enables the selective reduction of the nitro group by adjusting the type of solvent. Moreover, ethylbenzene is rapidly synthesized from styrene in methanol within 5 min and can also be obtained under solvent-free conditions. The environmentally friendly and mild conditions employed during both material synthesis and catalytic hydrogenation processes contribute to making it an alternative green heterogeneous catalyst for hydrogenation reactions.