Structural Ni⁰–Ni^δ+ Pair Sites for Highly Active Hydrogenation of Nitriles to Primary Amines

Abstract

Supported metal pair sites have sparked interest due to their tremendous potential as bifunctional catalysts. Here, we report the structural Ni⁰-Ni^δ+ pair sites constructed in a well-defined nanocrystal phase of Ni₃P. These Ni⁰-Ni^δ+ pair sites exhibited a remarkable product formation rate of 123 mol_BA/mol_metal/h for the hydrogenation of benzonitrile (BN) to benzylamine (BA). The heterogeneity of surface Ni atoms over the Ni₃P crystal created two types of metal centers, Ni⁰ and Ni^δ+, with a specific spatial distance of 4-5 Å. The Ni⁰ site acted as the center for H₂ activation, while the Ni^δ+ site served as the adsorption and activation center for the C ≡ N group. The highly efficient cooperation effect of Ni⁰-Ni^δ+ pair sites resulted in a TOF of 2915 h^-1 in BN hydrogenation, which is 2.4 and 9.7 times higher than that over the mono-Ni⁰ and -Ni^δ+ sites, respectively.