Atomically Defined Pd ₂ -Cu ₁ Integrated Clusters Break the Activity–Selectivity Trade-Off in Alkyne Semihydrogenation

Designing catalytic systems that overcome the intrinsic trade-off between activity and selectivity remains a fundamental challenge in selective alkyne hydrogenation. Here, we report a preconstruction strategy (PCS) to precisely assemble Pd2-Cu1 integrated clusters (ICs) stabilized by ionic liquids, achieving fully exposed active sites with 100% atomic utilization. This rational design enables nearly complete conversion of acetylene with >99% ethylene selectivity and durability over 800 h of continuous operation. Compared to conventional impregnation methods, the PCS ensures atomic-level control over the coordination environment and electronic structure, as validated by advanced spectroscopy and density functional theory calculations. The optimized C2H2/C2H4 adsorption behavior and the tailored hydrogenation pathway over Pd2-Cu1 ICs significantly lower the energy barriers for key intermediates while suppressing overhydrogenation. This work establishes a generalizable bottom-up design principle for constructing atom-efficient, stable, and selective hydrogenation catalysts, offering a transformative route for the development of next-generation heterogeneous catalysts.