Synthesis and Characterization of a Highly Reactive and Robust Chlorine‐Bound Ni Single‐Atom‐Catalyst for the Continuous Flow Ring‐Opening Reaction of Epoxides

Abstract

Nickel single-atom-catalysts (NiÀ SACs), which are known for their unique catalytic activity, are mainly used in electrocatalytic reactions that focus on high metal loading in carbon support to improve their performance. However, we attempted to modify the Ni species to find new catalytic properties by hypothesizing that functionalized NiÀ SACs can exhibit strong Lewis acidic properties in organic reactions. Herein, a low-temperature saltassisted synthesis of highly Lewis acidic chlorine-bound nickel SAC (ClÀ NiÀ SAC) is established and the synthesized catalyst is applied to the ring-opening reaction of epoxides with alcohol. The obtained ClÀ NiÀ SAC facilitates a fast and efficient ringopening reaction of epoxides with high recyclability. In addition, the highly active ClÀ NiÀ SAC was applied to the continuous flow set-up for sustainable transformation for 24 h, yielding 9.7 g of the desired product. Stereochemical experiments and density functional theory calculations demonstrated the importance of MeOH•••Cl hydrogen bonding, NÀ H•••Ni agostic interaction, and π-stacking in the transition state.

Chemoselective Nitro Reduction Using Nitrogen‐Doped Carbon‐Encapsulated Ni Catalyst and Y‐Type Packed Bed Column for Continuous Flow Reaction

“…The catalyst, N‐doped carbon‐encapsulated nickel nanoparticles on a carbon substrate (Ni@N−C), was synthesized using a controlled pyrolysis process. Adenine was polymerized and carbonized in molten NiCl 2 salt to provide N‐rich carbon with a high Ni content in the form of single‐atom species of Ni bound to chlorine [59] . Subsequent calcination under inert conditions resulted in the Ni@N−C core‐shell catalyst.…”

“…Adenine was polymerized and carbonized in molten NiCl 2 salt to provide N-rich carbon with a high Ni content in the form of single-atom species of Ni bound to chlorine. [59] Subsequent calcination under inert conditions resulted in the Ni@NÀ C core-shell catalyst. A distinguishing feature of this synthetic method, compared to others, [60] is that the nitrogen and carbon components of the N-rich carbon support can undergo vaporization and coat Ni nanoparticle agglomerates with N-doped carbon, even without the need for an external carbon source (Figure 1a).…”