Intermetallic Ni2Si/SiCN as a highly efficient catalyst for the one-pot tandem synthesis of imines and secondary amines

Abstract

Based on the isolation of the active sites in the crystal structure as well as the strong alteration of the electronic structure in comparison to elemental metals, metal silicides as typical intermetallic compounds have boosted their applications in catalysis. Heterogeneous Ni₂Si/SiCN as a promising and low-cost catalyst alternative to noble-metals has been successfully synthesized via the chemical modification of a polysilazane precursor at a molecular level by the use of metal complexes followed by its temperature-programmed pyrolysis. In the one-pot tandem synthesis of imines and secondary amines via the reductive coupling of nitrobenzene and benzaldehyde, the as-prepared Ni₂Si/SiCN-1000 catalyst exhibits excellent catalytic performance (conversion >99% and selectivity to aromatic amine >92%) and excellent recyclability under optimal reaction conditions. Due to the reduction induction support–metal strong interactions and the formation of intermetallic Ni₂Si, the electronic structure of the metallic Ni active site has been modified, which may tone the catalytic performance and enhance the stability of the catalyst.