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PleaseRd So Cn oA t da vd aj un s ct ems argins
DOI: 10.1039/C6RA21415K
Journal Name
600-2h) and Co@NC (700-2h), which indicated that the Co(0)
ARTICLE
(
Notes and references
was important for the reductive amination. From XPS, we can
also see the peaks of Co(0). Additionally, the formation of
graphitic carbon nitride structure may play a role for the
stability, activity and selectivity of the Co@NC (800-2h)
catalyst. In catalysts Co@NC (800-2h) and Co@NC (700-2h), we
can see a wide peak at about 25 degree. The imidazole
1
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,
7
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o
17
structure can be remained after pyrolysis at 800 C, which
may be beneficial to the catalyst Co@NC (800-2h). The N-
doped carbon provided suitable coordination structure for the
Co active center, and then the Co@NC (800-2h) exhibited high
activity and selectivity for the reductive amination. As we can
7
906.
see peaks of metallic β-Co but no peaks for CoO or Co
3 4
O in
3
4
(a) H. Kimura, Catal. Rev., 2011, 53, 1-90; (b) A. Monopoli, P.
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XRD spactra, we can image that the Co(0) particles were coated
2
+
with CoO in the Co@NC (800-2h). Moreover, the Co was
detected by XPS, which implied that the CoO was only thin
layer outside Co(0) particles. Thus, strong reaction conditions
were needed for the reductive amination by Co@NC (800-2h).
In addition, the Co catalyst Co@NC (800-2h) should has room
to be improved as the average diameter of the Co particles is
about 23 nm.
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Although strong reaction conditions are needed for the
reductive amination, the Co catalyst Co@NC (800-2h) is much
cheaper than noble metal catalysts, and the selectivity is
excellent even at high temperature. Moreover, the Co catalyst
is heterogeneous, and can be separated and reused easily,
which is superior to homogeneous catalysts. In addition, the
Co@NC (800-2h) can be applicable generally for the synthesis
of both secondary and tertiary amines, which may be used
widely for the practical synthesis of pharmaceuticals and bulky
chemicals.
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Conclusions
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In conclusion, a general reductive amination of aldehydes
and ketones with primary and secondary amines to related
secondary and tertiary amines was demonstrasted by Co@NC
8
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(800-2h) catalyst with H
2
gas. The active and selective Co
9
1
catalyst Co@NC (800-2h) was prepared and characterized.
Various secondary and tertiary amines were synthesized in
high yield without any additives by the Co catalyzed reductive
amination of aldehydes and ketones. Moreover, biologically
2
205-2209; (b) L. He, L. Zhao, D. X. Wang and M. X. Wang,
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was reusable at least 5 times without obvious deactivation.
1
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Acknowledgements
This work was supported by the National Natural Science of
Foundation of China (grant No. 21676140), the fund from the
State Key Laboratory of Materials-Oriented Chemical
Engineering (grant ZK201402) and the Project of Priority
Academic Program Development of Jiangsu Higher Education
Institutions (PAPD).
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