Hydrotalcite-Supported Cobalt Phosphide Nanorods as a Highly Active and Reusable Heterogeneous Catalyst for Ammonia-Free Selective Hydrogenation of Nitriles to Primary Amines
Min Sheng, Sho Yamaguchi, Ayako Nakata, Seiji Yamazoe, Kiyotaka Nakajima, Jun Yamasaki, Tomoo Mizugaki, Takato Mitsudome
Abstract
Traditional non-noble-metal catalysts for the hydrogenation of carboxylic acid derivatives have suffered from air instability and inadequate activity, requiring delicate catalyst handling and harsh reaction conditions. Thus, the development of non-noble-metal-based catalysts with both air stability and high activity has recently received much attention. We herein report hydrotalcite-supported cobalt phosphide nanorods (Co2P NR/HT) acting as an air-stable, active, and reusable non-noble-metal-based heterogeneous catalyst for the selective hydrogenation of nitriles to the corresponding primary amines. Co2P NR/HT exhibits a broad substrate generality, including sulfur-containing nitriles as well as aromatic, heteroaromatic, aliphatic, and dinitriles, under mild conditions, typically merely 1 bar of H2 atmosphere. Moreover, the high activity of Co2P NR/HT enabled nitrile hydrogenation under ammonia-free conditions, affording primary amines in high yields. The used Co2P NR/HT catalyst was recoverable and reusable without any significant loss in activity or selectivity, thus demonstrating the high performance of the Co2P NR/HT catalyst. Density functional theory (DFT) calculation results indicate that Co2P NR activates a nitrile at the surface through the back donation of d-electrons in Co2P NR to C≡N moiety, facilitating the nitrile hydrogenation to the primary amine.