Cobalt single-atom catalysts for domino reductive amination and amidation of levulinic acid and related molecules to N-heterocycles

Nanoparticles and single atoms of cobalt synergistically enabled low-temperature reductive amination of carbonyl compounds

“…We can assume that they could not play a catalytic role in the reaction process because it was very difficult for them to contact with the reactants due to the limited mass transfer. 41 These results above confirmed the coexistence of metallic Co and atomically dispersed Co–N x sites in Co@C–N(800). When using Co@C–N(800)–H + as the catalyst, only very small amounts of Schiff bases were generated ( Table 1 , entry 11), indicating poor catalytic activity of Co@C–N(800)–H + in the hydrogenation step of the reaction process.…”

“…S11 †) of Co@C-N(800) show that there was a strong Co-Co coordination peak (at about 2.18 Å), resulting in a weak Co-N coordination peak (at about 1.46 Å), which is a general phenomenon when metal nanoparticles and signal metal atoms simultaneously exist. 41 As discussed above, the Co-N coordination peak was signicantly improved aer most of the Co nanoparticles were removed (Fig. S11 †).…”

“…It is known that Co nanoparticles could be easily removed using HCl solution. 41 Thus, it can be deduced that the remaining Co nanoparticles in Co@C–N(800)–H + (the treated catalyst with HCl solution for 48 h) were wrapped in the C–N support. We can assume that they could not play a catalytic role in the reaction process because it was very difficult for them to contact with the reactants due to the limited mass transfer.…”

“…When using Co@C–N(800)–H + as the catalyst, only very small amounts of Schiff bases were generated ( Table 1 , entry 11), indicating poor catalytic activity of Co@C–N(800)–H + in the hydrogenation step of the reaction process. 41 Second, the C–N composite could be removed by treating Co@C–N(800) in air at 400 °C for 1 h and then 1 h under a H 2 /Ar atmosphere (containing 90% Ar) (Table S2 † ), and the resultant material was denoted as Co@C–N(800)–air. 40 The XPS spectra of Co@C–N(800)–air indicated that the signal of N was very weak (Fig.…”

Synergy between homogeneous and heterogeneous catalysis

“…Very recently, Beller and Jagadeesh et al 78 reported the preparation of Co-single atoms (0.75Co-phen@C-800-HCl) as reductive amination and amidation catalysts by the immobilization and pyrolysis of the Co–phenanthroline complex on carbon and subsequent washing with HCl to remove larger particles (Fig. 21).…”