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COMMUNICATION
DOI: 10.1039J/Co4uCrCn0a9l2N28aGme
catalyzed reduction in water is extremely fast, which resulted
completely reduced product (amine), however, in ethanol the
reduction process is slow enough to produce the coupling product
(azo). Initially, nitrobenzene reduced to nitrosobenzene (rate
constant; k1), which further reduced to aniline (k2). In ethanol, the
rate of second reduction is slower (k1 > k2) which resulted in the
accumulation of nitroso intermediate. Thus, amine compound
produced in the reaction further reacted with nitroso intermediate to
yield azo product through water elimination (see ESI). In the
presence of only NaBH4, the formation of nitroso is extremely slow
compared to Au@MOF-3 catalyzed reaction and the second
1
(a) K. J. Klabunde and Richards, R. M., in Nanoscale Materials in
Chemistry, John Wiley & Sons, Inc., 2009, pp. 771; (b) A.
Dhakshinamoorthy and H. Garcia, Chem. Soc. Rev., 2012, 41, 5262;
(c) M. O’Keeffe and O. M. Yaghi, Chem. Rev., 2011, 112, 675; (d)
M. Zhao, K. Deng, L. He, Y. Liu, G. Li, H. Zhao and Z. Tang, J. Am.
Chem. Soc., 2014, 136, 1738; (e) G. Li, H. Kobayashi, J. M. Taylor,
R. Ikeda, Y. Kubota, K. Kato, M. Takata, T. Yamamoto, S. Toh, S.
Matsumura and H. Kitagawa, Nat. Mater., 2014, 13, 802.
2
3
(a) S. Kitagawa, R. Kitaura and S.ꢀi. Noro, Angew. Chem. Int. Ed., 2004,
43, 2334; (b) J.ꢀR. Li, J. Sculley and H.ꢀC. Zhou, Chem. Rev., 2011, 112,
869; (c) J. R. Long and O. M. Yaghi, Chem. Soc. Rev., 2009, 38, 1213.
(a) K. Na, K. M. Choi, O. M. Yaghi and G. A. Somorjai, Nano Letters,
2014, 14, 5979; (b) C.ꢀH. Kuo, Y. Tang, L.ꢀY. Chou, B. T. Sneed, C. N.
Brodsky, Z. Zhao and C.ꢀK. Tsung, J. Am. Chem. Soc., 2012, 134,
14345; (c) W. Zhang, G. Lu, C. Cui, Y. Liu, S. Li, W. Yan, C. Xing, Y.
R. Chi, Y. Yang and F. Huo, Adv. Mater., 2014, 26, 4056; (d) P.
Pachfule, M. K. Panda, S. Kandambeth, S. M. Shivaprasad, D. D. Diaz
and R. Banerjee, J. Mater. Chem. A, 2014, 2, 7944; (e) P. Pachfule, S.
Kandambeth, D. D. Diaz and R. Banerjee, Chem. Commun. 2014, 50,
3169.
1
reduction to amine is almost negligible as observed from the Hꢀ
NMR spectroscopy (Fig. S22). This control experiment showed that
the direct involvement of the AuꢀNPs into the catalytic process.
When the Au@MOFs catalytic reductions of 4ꢀNP and 2,4ꢀDNP
were carried out in water, the second reduction process is expected
to be much faster than the first reduction due to the higher
dissociation of NaBH4 in water compared to ethanol. Therefore, in
water the reduced product is exclusively amine and also the
conversion rate is extremely fast.
Table 3. Au@MOF-3 catalyzed conversion of aromatic nitro to the
corresponding azoꢀderivatives.
4
5
(a) M. Meilikhov, K. Yusenko, D. Esken, S. Turner, G. Van
Tendeloo and R. A. Fischer, Eur. J. Inorg. Chem., 2010, 2010, 3701;
(b) A. Aijaz and Q. Xu, J. Phys. Chem. Lett., 2014, 5, 1400.
(a) S. Hermes, M.ꢀK. Schröter, R. Schmid, L. Khodeir, M. Muhler, A.
Tissler, R. W. Fischer and R. A. Fischer, Angew. Chem. Int. Ed., 2005,
44, 6237; (b) T. Ishida, M. Nagaoka, T. Akita and M. Haruta, Chem.
Eur. J., 2008, 14, 8456; (c) H.ꢀL. Jiang, Q.ꢀP. Lin, T. Akita, B. Liu, H.
Ohashi, H. Oji, T. Honma, T. Takei, M. Haruta and Q. Xu, Chem. Eur.
J., 2011, 17, 78; (d) D. Esken, S. Turner, O. I. Lebedev, G. Van
Tendeloo and R. A. Fischer, Chem. Mater., 2010, 22, 6393; (e) H.ꢀL.
Jiang, B. Liu, T. Akita, M. Haruta, H. Sakurai and Q. Xu, J. Am. Chem.
Soc., 2009, 131, 11302; (f) F. Schröder, D. Esken, M. Cokoja, M. W. E.
van den Berg, O. I. Lebedev, G. Van Tendeloo, B. Walaszek, G.
Buntkowsky, H.ꢀH. Limbach, B. Chaudret and R. A. Fischer, J. Am.
Chem. Soc., 2008, 130, 6119.
Entry
Reactant (R1, R2)
H, H
Product (R1, R2)
H, H
Yield (%)
1
2
3
4
5
6
7
78
67
85
56
83
85
92
Me, H
OMe, H
OH, H
Br, H
CO2Me, H
H, Ph
Me, H
OMe, H
OH, H
Br, H
CO2Me, H
H, Ph
In conclusions, loading of exceptionally large amount of MNPs into
MOFs without altering monodispersity and particle size has been
successfully achieved by clever functionalization of pores of MOFs.
The alkyne functionalized MOFs have been utilized for stabilization
of exceptionally large amount of AuꢀNPs (~50 wt %) by taking
advantage of distinct πꢀdonation and πꢀacceptor characteristics of
alkyne functionalities with Au3+ ions. The stepwise formation of NPs
i.e. adsorption of metal ions inside MOFs and subsequent reduction
to NPs was monitored by direct SEMꢀEDAX mapping and TEM
analysis, respectively. These MOFs supported AuꢀNPs (Au@MOFs)
were further employed as efficient heterogeneous catalysts for
reduction of 4ꢀNP and 2,4ꢀDNP in the presence of NaBH4 and water
as solvent. The catalytic activity obtained in our case is much
superior compared to other supported AuꢀNPs as catalysts reported
earlier. The mechanism of completely different reduction behavior
of aromatic nitro compounds in ethanol has been investigated by
time dependent 1HꢀNMR spectroscopy. This promising new concept
of introducing terminal alkyne into is expected to be very useful for
the development of superior catalysts.
6
7
G. Lu, S. Li, Z. Guo, O. K. Farha, B. G. Hauser, X. Qi, Y. Wang, X.
Wang, S. Han, X. Liu, J. S. DuChene, H. Zhang, Q. Zhang, X. Chen,
J. Ma, S. C. J. Loo, W. D. Wei, Y. Yang, J. T. Hupp and F. Huo, Nat.
Chem., 2012, 4, 310.
A. Aijaz, A. Karkamkar, Y. J. Choi, N. Tsumori, E. Rönnebro, T.
Autrey, H. Shioyama and Q. Xu, J. Am. Chem. Soc., 2012, 134, 13926.
S. J. Toal and W. C. Trogler, J. Mater. Chem., 2006, 16, 2871.
(a) Z. Zhang, C. Shao, P. Zou, P. Zhang, M. Zhang, J. Mu, Z. Guo, X. Li,
C. Wang and Y. Liu, Chem. Commun., 2011, 47, 3906; (b) A. Gangula,
R. Podila, R. M, L. Karanam, C. Janardhana and A. M. Rao, Langmuir,
2011, 27, 15268; (c) H. Xu, X. Chen, J. Gao, J. Lin, M. Addicoat, S. Irle
and D. Jiang, Chem. Commun. 2014, 50, 1292.
8
9
10 Z. D. Pozun, S. E. Rodenbusch, E. Keller, K. Tran, W. Tang, K. J.
Stevenson and G. Henkelman, J. Phys. Chem. C, 2013, 117, 7598.
11 (a) F. Ke, J. Zhu, L.ꢀG. Qiu and X. Jiang, Chem. Commun., 2013, 49,
1267; (b) H.ꢀL. Jiang, T. Akita, T. Ishida, M. Haruta and Q. Xu, J. Am.
Chem. Soc., 2011, 133, 1304.
PSM is grateful to the DST, India for financial support.
Notes and references
aDepartment of Inorganic and Physical Chemistry, Indian Institute of
Science, Bangalore, India. Fax: (+91)80-2360-1552; Tel: (+91)80-2293-
Electronic Supplementary Information (ESI) available: Materials, general
synthesis procedure, characterization, crystallographic data, detailed catalysis
procedure, detailed mechanistic investigations. See DOI: 10.1039/c000000x/
4 | J. Name., 2012, 00, 1-3
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