(198d) Structural Pair Sites for Highly Active Hydrogenation of Nitriles

Heterogeneous metal catalysis typically involves multiple steps, including adsorption, surface reactions, and desorption, requiring bifunctional active sites to optimize reactivity across all stages. These sites enable the efficient transformation of reactants by having distinct centers for different reaction steps. However, designing catalysts with well-defined bifunctional sites remains challenging, as it requires precise control over the spatial arrangement of these active sites at the sub-nanoscale.

Here, we present a novel strategy for constructing metal pair-sites with heterogeneous centers, Ni⁰ and Ni^δ⁺, within the crystal phase of metal-rich Ni₃P. These Ni⁰-Ni^δ⁺ pair-sites exhibit a specific distance of 4–5 Å, creating a cooperative effect that enhances catalytic performance in hydrogenation reactions. Using benzonitrile hydrogenation as a model, we demonstrate the high efficiency of these pair-sites in selectively producing primary amines. Compared to monofunctional Ni and Ni₂P catalysts, Ni₃P shows superior activity, attributed to its well-defined Ni⁰-Ni^δ⁺ sites. Our integrated reaction experiments, in situ FTIR analysis, and DFT calculations reveal the distinct roles of each site: Ni⁰ activates H₂, while Ni^δ⁺ adsorbs and activates the C≡N group, resulting in synergistic catalysis.

This study offers a new perspective on bifunctional catalyst design, emphasizing the role of well-defined metal pair-sites in hydrogenation reactions. The findings highlight the potential of Ni⁰-Ni^δ⁺ pair-sites in Ni₃P for efficient, cost-effective, and selective nitrile hydrogenation, opening avenues for broader applications in the fine chemical industry.