Origin of the Activity of Co–N–C Catalysts for Chemoselective Hydrogenation of Nitroarenes

Abstract

The production of functionalized anilines by chemoselective hydrogenation of nitroarenes occupies an important position in the chemical industries. Recently, cobalt and nitrogen codoped carbon (Co–N–C) catalysts have been reported to show outstanding catalytic performance in this process, whereas the nature of their active sites is still at the center of intense debate. In this paper, based on the well-controlled experiments on four types of typical Co–N–C materials derived from different methodologies, several unusual generalities in the hydrogenation of nitroarenes are clearly revealed, including protic-solvent dependence, antipoisoning, acid resistance, and reversible deactivation. Further investigations indicate that the single-atom species Co–N x are the main active sites of the Co–N–C catalysts in this chemoselective hydrogenation process. The present work sheds light on the mechanism study on the metal–N–C catalysts and further contributes to the rational design of the high-performance single-atom catalysts.

Reductive Formylation of Nitroarenes using HCOOH over Bimetallic C−N Framework Derived from the Integration of MOF and COF

“…SCN − masks the active sites by coordinating with metal centers in the catalyst and deactivate the catalyst. Whereas the CoOx and larger Co nanoparticles are reported to exhibit no effect with the KSCN poisoning test [46,48] . This experiment suggests that the small nanoclusters are present in the catalyst, which further confirms the results obtained from TEM.…”

“…Whereas the CoOx and larger Co nanoparticles are reported to exhibit no effect with the KSCN poisoning test. [46,48] This experiment suggests that the small nanoclusters are present in the catalyst, which further confirms the results obtained from TEM. The catalytic poisoning test confirms that the catalytic activity is mainly due to the presence of Co-Nx and Co nanoclusters.…”

“…The HCOOH at elevated temperature (>393 K) preferentially decomposes under the dehydration (HCOOH CO+H 2 O) pathway. Hence the chance of forming the formylated product via an indirect pathway is more (Discussed later in the mechanism section) [45,48] . Thus, the reactions are performed at four different reaction temperatures in the range of 393 K to 423 K (Figure 3C).…”

“…Hence the chance of forming the formylated product via an indirect pathway is more (Discussed later in the mechanism section). [45,48] Thus, the reactions are performed at four different reaction temperatures in the range of 393 K to 423 K (Figure 3C). With an increase in the temperature, formanilide selectivity increases.…”

Highly Dispersed CoNi Alloy Embedded in N‐doped Graphitic Carbon for Catalytic Transfer Hydrogenation of Biomass‐derived Furfural

“…It has been reported that the N‐doped carbon shell modified by metal NPs and the embedded metal NPs could be respectively served as catalytic active species for H 2 activation during the hydrogenation reactions [34,37] . Moreover, the strong interaction between embedded metal NPs and N‐doped carbon shell in the well‐defined structure could induce the formation of novel active species such as metal‐N species at the interface [38,39] . Besides, if the embedded metal NPs are bimetallic alloys, the synergistic effect enabled by two different metal components can further enhance the catalytic performance [40–42] .…”