Palladium atom-pair catalyst derived from a molecular palladium polyhedron for alkyne semi‑hydrogenation

Within the field of selective alkyne hydrogenation, Pd-based catalysts have shown high potential. Dual-atom catalysts (DACs) have emerged as a highly promising catalyst class, as they can integrate the outstanding selectivity typically associated with single-atom catalysts and the superior reactivity generally exhibited by metal nanoparticles. However, controllable synthesis of Pd DACs remains a major challenge. Here, we present a precursor-preorganization approach that employs a Pd₄L₄ metal-organic polyhedron (MOP) to generate Pd dual-atom sites. Upon thermal treatment, the MOP decomposes and the released Pd species are anchored onto g-C₃N₄ nanosheets (CN-NS), ultimately affording atomically well-defined Pd atom pairs (Pd₂/CN-NS). At 303 K and 1 bar H₂, Pd₂/CN-NS achieves 100% conversion of phenylacetylene while preserving a styrene selectivity of 94%. This performance significantly outperforms Pd single atoms (19% conversion), Pd nanoparticles (13% styrene selectivity), and the commercial Lindlar catalyst (56% conversion). Such a performance is ascribed to the cooperative effect between adjacent Pd sites. Moreover, Pd₂/CN-NS demonstrates broad applicability in the selective hydrogenation of diverse alkynes.