Highly selective and robust single-atom catalyst Ru1/NC for reductive amination of aldehydes/ketones

Abstract

Single-atom catalysts (SACs) have emerged as a frontier in heterogeneous catalysis due to the well-defined active site structure and the maximized metal atom utilization. Nevertheless, the robustness of SACs remains a critical concern for practical applications. Herein, we report a highly active, selective and robust Ru SAC which was synthesized by pyrolysis of ruthenium acetylacetonate and N/C precursors at 900 °C in N2 followed by treatment at 800 °C in NH3. The resultant Ru1-N3 structure exhibits moderate capability for hydrogen activation even in excess NH3, which enables the effective modulation between transimination and hydrogenation activity in the reductive amination of aldehydes/ketones towards primary amines. As a consequence, it shows superior amine productivity, unrivalled resistance against CO and sulfur, and unexpectedly high stability under harsh hydrotreating conditions compared to most SACs and nanocatalysts. This SAC strategy will open an avenue towards the rational design of highly selective and robust catalysts for other demanding transformations.

Advances in the Catalytic Reductive Amination of Furfural to Furfural Amine: The Momentous Role of Active Metal Sites

“…It is worth noting that the reductive amination of FUR generally encounters unfavorable side reactions, including the formation of difurfuryl amine (DFA), furfurine (FFI), and FUL, thus leading to a decline in the selectivity towards FUA. [37] To suppress the undesired reaction pathways and to enhance the FUA yield, understanding the energy level and stability of various products that form during the reductive amination of FUR becomes crucial. In regard to this, Komanoya et al [36] proposed a free-energy diagram of various imine and amine intermediates/products derived from FUR through density functional theory (DFT) calculations, demonstrating thermodynamically lesser stability of FUA compared to other byproducts such as FDA, DFA, and TFA (Scheme 2).…”

“…The higher basic character of support increases the electron density on the metal, favoring H 2 activation by HÀ H bond breaking, which plays an essential role in product selectivity, although not entailing in the ratedetermining step. [37] Figure 2 exemplifies the activity of Ru on different supports on the yield of FUA, displaying that the basic support TiP played a crucial role along with Ru, giving more The role of the differential proportion of Ru 0 and RuO 2 species in Ru on boron nitride (Ru/BN) on the reductive amination of FUR was investigated by XPS analysis. [49] XPS spectra of Ru/BN-e (e represents Ru on the edges of the boron nitride network) disclose the existence of 59 % Ru 0 (460.9 eV) and 41 % Ru n + (462.5 eV), affording a maximum yield of 95.9 % FUA (4 equiv.…”

“…Regarding this, Ru incorporated an N-doped carbon network of single-atom catalyst to yield RuN x species (RuN 5 , RuN 4 , and RuN 3 ) in RuN x C y was developed by simply changing the pyrolysis temperature (700-1000 °C). [37] Ru 1 /NC-700 (pyrolyzed at 700 °C), having RuN 5 structure, yielded no FUA from FUR with a large amount of trimerized imine intermediate hydrofuramide (HFA), indicating insignificant hydrogenation activity. As the pyrolysis temperature increased to 800 °C, Ru 1 / NC-800 with RuN 4 structure afforded 43 % of FUA, which increased to 84 % with Ru 1 /NC-900 (pyrolyzed at 900 °C), having RuN 3 structure, indicating enhanced hydrogenation activity due to the changes in the electronic interaction between Ru and N.…”

Single-atom catalysts for thermal- and electro-catalytic hydrogenation reactions

“…For example, Zhang and co-workers synthesized Ru/NC SACs by pyrolysis of ruthenium acetylacetonate and C, N-containing precursors for the reductive amination of aldehydes/ketones. 59 When the pyrolysis temperature is changed, both the Ru-N coordination structure (e.g., Ru 1 -N 5 , Ru 1 -N 4 , and Ru 1 -N 3 ) and the electron density of the Ru single atoms are varied, leading to different catalytic performance. As a consequence, the resulting Ru 1 -N 3 structure with the largest electron density exhibits moderate capability for hydrogen activation, which affords the highest activity and selectivity for the reductive amination of aldehydes/ketones to primary amines.…”

Hydride-like NH2δ- species-driven reductive amination over Co@CoO catalyst

“…[1][2][3][4][5][6][7] In the last decades, catalytic reductive amination of biomass-derived carbonyl compounds (furfural, cyclopentanone, HMF, etc.) to obtain primary amines has drawn particular attention, providing grand opportunities for the sustainable production of amines from renewable energy 1,2,5,[8][9][10][11][12][13] Scheme 1. Comparison of catalytic mechanisms between noble metal catalysts and Co@CoO.…”