Spike-Embedded Nanocatalysts via Metal-Directed Carbonization for Highly Efficient and Robust Semi-Hydrogenation

Achieving high catalytic efficiency while maintaining robust structural stability is a persistent dilemma in the design of carbon-supported nanocatalysts. Herein, we report a metal-directed carbonization strategy to resolve this trade-off by utilizing hierarchical organic microspheres as precursors. The pivotal role of metal ions (e.g., Pd²⁺) extends beyond serving as precursors for metallic active sites, as they also facilitate carbonization at reduced temperatures and help preserve the precursor morphology during calcination. This metal-assisted aromatic coupling process reduces carbonization temperature by 130°C and drives the migration of metal nanoparticles to the tips of the carbon spikes, where they become embedded within the carbon matrix and partially exposed. Consequently, the afforded catalyst is 84 times more active than Pd/C and 14 times more active than Pd/Al₂O₃ for semi-hydrogenation of nitrobenzene to azoxybenzene, and maintains high activity and selectivity even in the presence of ethylenediamine and thiourea. The catalyst also displays applicability in the semi-hydrogenation of alkynes to alkenes with excellent chemoselectivity. Overall, the templated strategy is general, extends to multiple metals and microsphere morphologies, and provides a scalable route to carbon-supported catalysts that combine site accessibility with nanoparticle stabilization for challenging, poison-prone reactions.