Single-Site Pd Coupling with Jahn-Teller Active Cu as Pair Sites for Simultaneous Activation of Alkyne and Hydrogen Toward Efficient Semihydrogenation

Abstract

Single-site pairs are promising in achieving high selectivity and activity in alkyne semihydrogenation, but its applicability is limited by the insufficient activity because pair sites cannot adsorb and activate alkyne. Here, we couple single-site Pd with Jahn-Teller active Cu atoms of Cu-doped Fe₂O₃ to construct a highly active and stable single-site Pd-Cu pairs. The Jahn-Teller active Cu possesses elongated axial orbitals, and the strong electronic coupling between Pd and Cu further contributes to their unoccupied axial d orbitals, which helps Pd-Cu pair to cooperatively activate C₂H₂ molecule, unlike ordinary single-site pairs where only H₂ is activated. As a result, this catalyst exhibits state-of-the-art performance, with > 99.99% conversion and 95.5% selectivity as well as excellent stability with negligible performance decay after 300-h test in purifying acetylene of ethylene stream. Both in situ spectra and theoretical results indicate two H addition steps occur on Pd and Cu sites in sequence. This work opens an avenue for constructing highly efficient single-site pairs for selective hydrogenation and beyond.

Keywords: Alkyne adsorption; Hydrogen activation; Palladium; Semihydrogenation of alkynes; Single‐site pair catalyst.