Unlocking enhanced selectivity of Pd/Al2O3 in semihydrogenation of alkynes by in situ ligand‐reduction strategy

Abstract The partial hydrogenation of alkynes into alkenes constitutes a pivotal chemical transformation in the synthesis of fine chemicals, pharmaceuticals, and polymers. Nevertheless, the extant industrial catalyst falls short of achieving a felicitous equilibrium between its catalytic potency and selectivity. Herein, triphenylphosphine (PPh 3 ) modified Pd/Al 2 O 3 catalysts are fabricated through a “one‐pot” process, which achieve highly selective hydrogenation of alkynes at room temperature. PPh 3 plays a dual role—as a reducing agent and a ligand. Kinetic and characterization studies reveal PPh 3 alters H 2 activation from homolytic to heterolytic cleavage, which facilitate the formation of alkene. Moreover, PPh 3 can also optimize the reaction microenvironment, achieving the reduced self‐poisoning of alkyne and promoted desorption of alkene. In the realm of alkyne hydrogenation, our philosophy encompasses a global optimization of active sites, ligand systems, and reaction microenvironmental. This method steers the course of catalyst development for other reactions beyond the field of alkyne hydrogenation.