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. 2021 Oct 26;12(1):6194.
doi: 10.1038/s41467-021-26542-y.

Tuning the selectivity of catalytic nitriles hydrogenation by structure regulation in atomically dispersed Pd catalysts

Zhibo Liu #  1   2 , Fei Huang #  2   3 , Mi Peng #  4 , Yunlei Chen #  5   6 , Xiangbin Cai  7 , Linlin Wang  1   2 , Zenan Hu  1 , Xiaodong Wen  5   6 , Ning Wang  7 , Dequan Xiao  8 , Hong Jiang  4 , Hongbin Sun  9 , Hongyang Liu  10   11 , Ding Ma  12
Affiliations

Tuning the selectivity of catalytic nitriles hydrogenation by structure regulation in atomically dispersed Pd catalysts

Zhibo Liu et al. Nat Commun. .

Abstract

The product selectivity in catalytic hydrogenation of nitriles is strongly correlated with the structure of the catalyst. In this work, two types of atomically dispersed Pd species stabilized on the defect-rich nanodiamond-graphene (ND@G) hybrid support: single Pd atoms (Pd1/ND@G) and fully exposed Pd clusters with average three Pd atoms (Pdn/ND@G), were fabricated. The two catalysts show distinct difference in the catalytic transfer hydrogenation of nitriles. The Pd1/ND@G catalyst preferentially generates secondary amines (Turnover frequency (TOF@333 K 709 h-1, selectivity >98%), while the Pdn/ND@G catalyst exhibits high selectivity towards primary amines (TOF@313 K 543 h-1, selectivity >98%) under mild reaction conditions. Detailed characterizations and density functional theory (DFT) calculations show that the structure of atomically dispersed Pd catalysts governs the dissociative adsorption pattern of H2 and also the hydrogenation pathway of the benzylideneimine (BI) intermediate, resulting in different product selectivity over Pd1/ND@G and Pdn/ND@G, respectively. The structure-performance relationship established over atomically dispersed Pd catalysts provides valuable insights for designing catalysts with tunable selectivity.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1
Fig. 1. Structural characterization of catalysts.
a HAADF-STEM images of Pd1/ND@G at low magnification. b Atomically dispersed single Pd atoms in Pd1/ND@G highlighted by the yellow circles. c HAADF-STEM images of Pdn/ND@G at low magnification. d Fully exposed Pd clusters in Pdn/ND@G highlighted by the red circles. e Pd K-edge XANES profiles and f EXAFS spectra for Pd1/ND@G and Pdn/ND@G. Scale bars: a, 5 nm; b, d, 2 nm; c, 20 nm.
Fig. 2
Fig. 2. Catalytic performances of Pd1/ND@G and Pdn/ND@G catalysts in transfer hydrogenation of benzonitrile.
a Possible reaction scheme in the transfer hydrogenation of benzonitrile yielding benzylamine, N-benzylidenebenzylamine, and dibenzylamine. b Time-conversion plot for production formation from the transfer hydrogenation of benzonitrile over Pd1/ND@G. Reaction conditions: solvent, methanol, 10 mL; BN, 0.5 mmol; catalyst, 30 mg; AB, 4 mmol; temperature, 60 °C. c Time-conversion plot for production formation from the transfer hydrogenation of benzonitrile over Pdn/ND@G. Reaction conditions: solvent, methanol, 10 mL; BN, 0.5 mmol; catalyst, 10 mg; AB, 3 mmol; temperature, 40 °C. d TOF over Pd1/ND@G (time, 15 min) and Pdn/ND@G (time, 5 min). e Product yield for transfer hydrogenation of benzonitrile over ND@G, Pd1/ND@G (time, 8 h), Pdn/ND@G (time, 30 min), and Pd/C (time, 30 min).
Fig. 3
Fig. 3. Substrate extension.
Catalytic performance of Pd1/ND@G and Pdn/ND@G catalyst in transfer hydrogenation of different substituted nitriles.
Fig. 4
Fig. 4. Step-by-step hydrogenation mechanism of benzonitrile to benzylamine on Pd1/ND@G and Pdn/ND@G.
Color code: Pd1/ND@G (green line) and Pdn/ND@G (blue line). Pd cyan, C gray, H white.
See this image and copyright information in PMC

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