Asymmetric Coupled Binuclear-Site Catalysts for Low-Temperature Selective Acetylene Semi-Hydrogenation.

Heterogeneous metal catalysts with bifunctional active sites are widely used in chemical industries. Although their improvement process is typically based on trial-and-error, it is hindered by the lack of model catalysts. Herein, we report an effective vacancy-pair capturing strategy to fabricate 12 heterogeneous binuclear-site catalysts (HBSCs) comprising combinations of transition metals on titania. During the synthesis of these HBSCs, proton-passivation treatment and step-by-step electrostatic anchorage enabled the suppression of single-atom formation and the successive capture of two target metal cations on the titanium-oxygen vacancy-pair site. Additionally, during acetylene hydrogenation at 20 °C, the HBSCs (e.g., PtPd-TiO) consistently generated more than two times the ethylene produced by their single-atom counterparts (e.g., Pd-TiO). Furthermore, the PtPd binuclear sites in PtPd-TiO were demonstrated to catalyze CH hydrogenation via a bifunctional active-site mechanism: initially CH chemisorb on the Pt site, then H dissociates and migrates from Pd to Pt, and finally hydrogenation occurs at the Pt-Pd interface.