Journal of Materials Chemistry A
Paper
LDH/Pd composite showed high activities in cross-coupling
reactions. Besides, the abundant Co(II) sites on the support
could capture and regenerate leached Pd species during the
reaction process, leading to excellent stability of the composite.
With its outstanding activity and stability, and the simple
preparation method that is ready to scale up, this catalyst will
probably be very competitive against other current commercial
available catalysts.
Acknowledgements
Fig. 6 The leaching and regeneration of Pd species during the reac-
tion process in the presence of the CoAl–LDH/Pd composite.
We thank the nancial support from the National Natural
Science Foundation of China (NSFC 21333009, 21121063) and
the Chinese Academy of Sciences (KJCX2-YW-N41).
concentration of Pd species in the mother liquid was still about
40 ppb.23 In this study, the Pd concentration in the mother
liquid was negligible (less than 5 ppb).
Notes and references
We propose that the excellent stability of the CoAl–LDH/Pd
composite catalyst can be ascribed to the following factors. On
the one hand, the key lies in the presence of abundant Co(II)
species in the CoAl–LDH/Pd composite. Pd leaching originates
from the catalytic cycle of the coupling reactions, in which Pd
sites changed between Pd (0) and Pd(II) states. Pd(II) species
then could leach from the Pd clusters and enter into the mother
liquid. Such a leaching process was inevitable on heterogeneous
Pd catalysts.49 However, in the case of the CoAl–LDH/Pd
composite, as schematically illustrated in Fig. 6, the leached
Pd(II) species can be captured and reduced to Pd (0) species
again by the abundant Co(II) sites on the CoAl–LDH support. In
other words, the CoAl–LDH/Pd composite can capture and
regenerate the leached Pd species in the reaction process. On
the other hand, the 3D hierarchical-structured CoAl–LDH
support with abundant surface groups such as hydroxyls, as well
as the strong metal–support interaction, can effectively stabilize
the Pd nanoclusters well, suppressing the leaching of Pd species
and the aggregation of Pd NPs during catalysis.
For practical aspects, the preparation method can be readily
scaled up to produce a large quantity of the catalyst material. In
a trial using a larger vessel of 4 L, about 200 g of CoAl–LDH
support was produced in one batch (Fig. S5†), and the CoAl–
LDH/Pd catalyst can be produced via in situ reaction using the
above CoAl–LDH as the support in another batch (Fig. S6†). The
catalytic ability of the scale-up catalyst was the same as that of
the lab-scale one.
1 M. Lamblin, L. Nassar-Hardy, J.-C. Hierso, E. Fouquet and
F.-X. Felpin, Adv. Synth. Catal., 2010, 352, 33.
´
´
2 A. Molnar, Chem. Rev., 2011, 111, 2251.
3 A. Fihri, M. Bouhrara, B. Nekoueishahraki, J.-M. Basset and
V. Polshettiwar, Chem. Soc. Rev., 2011, 40, 5181.
4 N. Kambe, T. Iwasaki and J. Terao, Chem. Soc. Rev., 2011, 40,
4937.
5 H. Li, C. C. C. Johansson Seechurn and T. J. Colacot, ACS
Catal., 2012, 2, 1147.
6 T. E. Barder, S. D. Walker, J. R. Martinelli and S. L. Buchwald,
J. Am. Chem. Soc., 2005, 127, 4685.
7 S. Li, Y. Lin, J. Cao and S. Zhang, J. Org. Chem., 2007, 72,
4067.
8 D.-H. Lee and M.-J. Jin, Org. Lett., 2010, 13, 252.
9 C. Deraedt and D. Astruc, Acc. Chem. Res., 2014, 47, 494.
10 M. Chtchigrovsky, Y. Lin, K. Ouchaou, M. Chaumontet,
M. Robitzer, F. Quignard and F. Taran, Chem. Mater., 2012,
24, 1505.
11 Y. M. A. Yamada, S. M. Sarkar and Y. Uozumi, J. Am. Chem.
Soc., 2012, 134, 3190.
12 B. Yuan, Y. Pan, Y. Li, B. Yin and H. Jiang, Angew. Chem., Int.
Ed., 2010, 49, 4054.
13 J. Huang, W. Wang and H. Li, ACS Catal., 2013, 1526.
´
14 S. Niembro, A. Shar, A. Vallribera and R. Alibes, Org. Lett.,
2008, 10, 3215.
15 N. J. S. Costa, P. K. Kiyohara, A. L. Monteiro, Y. Coppel,
K. Philippot and L. M. Rossi, J. Catal., 2010, 276, 382.
16 J. Liu, H. Q. Yang, F. Kleitz, Z. G. Chen, T. Yang, E. Strounina,
G. Q. Lu and S. Z. Qiao, Adv. Funct. Mater., 2012, 22, 591.
17 G. M. Scheuermann, L. Rumi, P. Steurer, W. Bannwarth and
4. Conclusions
¨
R. Mulhaupt, J. Am. Chem. Soc., 2009, 131, 8262.
In summary, we have developed a facile one-pot surfactant-free
solvothermal method to produce uniform 3D ower-like hier- 18 X.-H. Li, M. Baar, S. Blechert and M. Antonietti, Sci. Rep.,
archical-structured CoAl–LDH spheres. And the CoAl–LDH/Pd
composite can be obtained through in situ reduction between 19 O. Metin, S. Ho, C. Alp, H. Can, M. Mankin, M. Gultekin,
2013, 3, 1743.
¨
¨
the oxidative Pd precursor and the reductive CoAl–LDH support.
Due to monodispersed tiny Pd nanoclusters with clean surface, 20 H. Liu, C.-Y. Cao, F.-F. Wei, Y. Jiang, Y.-B. Sun, P.-P. Huang
strong metal–support interaction, and good mass transfer and and W.-G. Song, J. Phys. Chem. C, 2013, 117, 21426.
diffusion from the 3D hierarchical architecture with large 21 S. Sarina, H. Zhu, E. Jaatinen, Q. Xiao, H. Liu, J. Jia, C. Chen
M. Chi and S. Sun, Nano Res., 2013, 6, 10.
surface area and suitable mesoporous structures, the CoAl–
and J. Zhao, J. Am. Chem. Soc., 2013, 135, 5793.
12744 | J. Mater. Chem. A, 2014, 2, 12739–12745
This journal is © The Royal Society of Chemistry 2014