A Simple and Versatile Approach for the Fabrication of Paper-Based Nanocatalysts: Low Cost, Easy Handling, and Catalyst Recovery

Article abstract of DOI:10.1002/cctc.201600666

A versatile method for the preparation of efficient and reusable nanocatalysts involving the painting of a commercial filter paper with a Pd@CNT (CNT=carbon nanotubes) ink was herein explored. The resulting paper-based material provided excellent results in the semihydrogenation of alkynes and alkynols and could be recycled at least five times without loss of activity or selectivity.

Full text of DOI:10.1002/cctc.201600666

DOI: 10.1002/cctc.201600666
Communications
A Simple and Versatile Approach for the Fabrication of
Paper-Based Nanocatalysts: Low Cost, Easy Handling, and
Catalyst Recovery
Laura Montiel,[a] Jorge A. Delgado,[b] Marta Novell,[c] Francisco J. Andrade,[c]
Carmen Claver,[a, b] Pascal Blondeau,*[c] and Cyril Godard*[a, b]
A versatile method for the preparation of efficient and reusable
nanocatalysts involving the painting of a commercial filter
paper with a Pd@CNT (CNT=carbon nanotubes) ink was
herein explored. The resulting paper-based material provided
excellent results in the semihydrogenation of alkynes and alky-
nols and could be recycled at least five times without loss of
activity or selectivity.
paper as reusable catalysts for sequential cross-coupling and
hydrogenation reactions.[4c] Conventional filter paper is of in-
herent interest as a catalyst support, as it is cost effective, bio-
degradable, accessible, and flexible. It, therefore, simplifies the
handling of the catalyst, for example, by manipulation with
tweezers, as well as the recycling process. Oleylamine-capped
Pd nanoparticles absorbed on paper were reported to provide
reusable catalysts for Suzuki cross-coupling and nitro-to-amine
reduction.[4d] These results show that such supports can be effi-
cient, although in these examples, the synthetic strategies
were complex (covalent grafting of the catalyst)[4] or limited to
a certain type of NP stabilizer to provide interactions with the
support.[4c,d] To overcome this latter drawback, the use of an in-
terface between the nanocatalyst and the support appears
promising, as it would allow the utilization of any type of sta-
bilizer. Carbon nanotubes present great potential for this role[5]
owing to their chemical stability, suitable porous properties,
and broad functionalization strategies (covalent and noncova-
lent).[6] In some cases, their structure also leads to metal–sup-
port interactions that can enhance the activity/selectivity of
the catalysts.[7] In addition, multiwalled carbon nanotubes de-
posited by chemical vapor deposition on silicon chips followed
by decoration with Pd to form a catalyst support membrane
was previously reported.[8]
The development of sustainable processes with minimal envi-
ronmental impact has been recognized as one of the major
challenges of this century.[1] In this context, heterogeneous cat-
alysis appears as a key tool to achieve the suitable utilization
of resources and to preserve and rehabilitate our environ-
ment.[2] Moreover, the application of metal nanoparticles (NPs)
as catalysts is of particular interest to maximize the available
metal surface area and, consequently, to enhance catalyst
productivity.
Nanocatalysts are usually immobilized on oxides such as
silica or alumina, on polymers, or on carbon materials.[3] How-
ever, the immobilization of selective catalysts onto cheap and
easy-to-handle solid supports is still of general interest, and re-
cently, alternative carriers such as textile, paper, and cotton
were demonstrated to be very attractive.[4] For instance, the
covalent immobilization of chiral organocatalysts on nylon was
reported with excellent stability, reactivity, and recyclability, to-
gether with flexibility and cost efficiency of the support.[4b] This
organotextile was used in several reactions such as the acyla-
tion of phenols to the esters and in the desymmetrization of
anhydrides with very good enantioselectivity. More recently,
Nagashima and co-workers reported polycationic salt stabilized
palladium nanoparticles immobilized on both cotton and
In the present communication, we describe the use of
carbon nanotubes (CNTs) as an interface between the metal
NPs and the support: the palladium nanoparticles were first
grown onto the nanotubes (Pd@CNT), and the resulting hybrid
material was subsequently anchored onto paper by simple
painting of a Pd@CNT ink (Figure 1).[9] This general approach is
simple, versatile, and easily scalable (by printing process of the
ink). The paper-based nanocatalyst was applied in the semihy-
drogenation of alkynes and alkynols; excellent catalytic per-
formance was observed and the nanocatalyst could be used
over at least five consecutive runs without loss of either activi-
ty or selectivity. The Pd nanoparticles were synthesized by
a one-pot method involving the decomposition of Pd2(dba)3
(dba=dibenzylideneacetone) under an atmosphere of H2 in
the presence of tricyclohexylphosphine (PCy3) and multiwalled
carbon nanotubes (MWCNTs) (Figure 1a).[10] TEM analysis of the
resulting hybrid material (Figure 2a) evidenced the homogene-
ous deposition of small PdNPs with a narrow size distribution
[(2.4Æ0.9) nm] onto the surface of the CNTs. Thermogravimet-
ric analysis revealed that these Pd@CNT hybrids exhibited
a content of palladium of approximately 35 wt% (Figure S1 in
the Supporting Information).
[a] L. Montiel, Prof. C. Claver, Dr. C. Godard
Departament de Quꢀmica Fꢀsica i Inorgꢁnica
Universitat Rovira i Virgili
C/Marceli Domingo 1, 43007 Tarragona (Spain)
E-mail: cyril.godard@urv.cat
[b] Dr. J. A. Delgado, Prof. C. Claver, Dr. C. Godard
Centre Tecnologic de la Quꢀmica
C/Marceli Domingo, 43007 Tarragona (Spain)
[c] Dr. M. Novell, Dr. F. J. Andrade, Dr. P. Blondeau
Departament de Quꢀmica Analꢀtica i Quꢀmica Orgꢁnica
Universitat Rovira i Virgili
C/Marceli Domingo 1, 43007 Tarragona (Spain)
E-mail: pascal.blondeau@urv.cat
Supporting Information for this article can be found under http://
dx.doi.org/10.1002/cctc.201600666.
ChemCatChem 2016, 8, 1 – 5
1
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
These are not the final page numbers! ÞÞ

Communications
Subsequently, the preparation of the paper-based nanocata-
lyst was performed manually by painting a conventional filter
paper. First, an ink was prepared by sonicating an aqueous
mixture of Pd@CNT and sodium dodecylbenzenesulfonate
(SDBS) (Figure 1b). The resulting suspension was then painted
onto the paper to afford the paper-based nanocatalyst (Fig-
ure 1c).[9] Figure 2b displays the ESEM/EDX (environmental
scanning microscopy/energy-dispersive X-ray spectroscopy) mi-
crograph of the paper, for which the homogeneous dispersion
of Pd (red spots) at the surface of the cellulose fibers is evi-
denced. Inductively coupled plasma (ICP) analysis of the paper
painted with 3, 7, and 10 layers of the Pd@CNT ink revealed Pd
contents of 0.15, 0.23, and 0.31 wt%, respectively. Notably, the
amount of Pd could be tuned by varying the number of ink
layers. The range of Pd loadings in these materials is compara-
ble to that of the method reported by Nagashima.[4c]
The paper-based catalyst painted with 7 layers was em-
ployed in the semihydrogenation of alkynes and alkynols,
which is a process of industrial relevance.[3] In a typical catalytic
experiment, a piece of paper was placed in a tube containing
the corresponding substrate in THF. The system was then pres-
surized with hydrogen (0.1–1.0 MPa) and heated (30/508C)
under stirring. After the reaction, the catalytic material was re-
moved by using tweezers, and the organic phase was analyzed
by GC–MS.
Figure 1. General approach for the preparation of the paper-based nanoca-
talyst: a) nanoparticles are grown on the surface of the CNTs to afford the
Pd@CNT hybrid, b) the hybrid is mixed with a surfactant to produce the
Pd@CNT ink, c) a filter paper is painted with Pd@CNT, d) the paper catalyst is
used for the semihydrogenation of alkynes, e) the catalyst is washed and re-
cycled over several reactions.
The experimental conditions (pressure, temperature, and
time) were initially optimized for a series of terminal and
internal alkynes and alkynols (Tables S1–S3).[11] If necessary,
quinoline was used as an additive, and its concentration
was optimized for each substrate.[12] Excellent selectivity to al-
kenes at high conversions was achieved for both alkyne and al-
kynol substrates by using this new paper-based catalyst.
Milder reaction conditions were required for the partial hydro-
genation of terminal alkynes (0.3 MPa H2, 308C) than for the
partial hydrogenation of internal alkynes or alkynols (0.5 MPa
H2, 508C).
The promising features of the new paper-based catalyst
prompted us to explore the scope of substrates that could be
selectively transformed. A series of terminal/internal alkynes
and alkynols were therefore tested (Table 1). For alkylic termi-
nal alkynes (Table 1, entries 1 and 2), excellent selectivities
were obtained for heptyne and octyne at full conversions (89
and 97%, respectively). In addition, conversion, selectivity, and
composition of the reaction mixture were plotted as a function
of time for 1-heptyne as a substrate (Figure S4). Upon compar-
ing the reactivities of 1-octyne, 2-octyne, and 4-octyne
(Table 1, entries 2–4), a decrease in the conversion from 100 to
56% was observed if the triple bond was internal, whereas the
alkene selectivity increased from 89 to 100%. These results can
be related to accessibility issues of the substituted triple
bonds, as previously proposed.[13]
Interestingly upon testing 4-octyne under stronger condi-
tions (508C, 0.5 MPa H2, 2 h; Table 1, entry 5), 98% conversion
was reached and full selectivity to the alkene was maintained.
In the semihydrogenation of phenylacetylene and cyclohexyla-
cetylene (Table 1, entries 6 and 7), lower conversion was mea-
sured for the aromatic alkyne (62 vs. 87%), whereas the alkene
Figure 2. a) TEM image of Pd@CNT and b) ESEM image of the paper-based
nanocatalyst (the red spots correspond to PdNPs deposited onto MWCNTs).
Scale bars=a) 20 nm, b) 500 nm.
&
ChemCatChem 2016, 8, 1 – 5
www.chemcatchem.org
2
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Communications
Table 1. Substrate scope for the selective hydrogenation of alkynes and
alkynols catalyzed by the paper-based catalyst.[a]
Entry
R1
R2
Conv.
[%]
Select. [%]
A (isomer% or cis%)
B
1[b]
CH3(CH2)4
CH3(CH2)5
CH3(CH2)4
CH3(CH2)2
CH3(CH2)2
Ph
H
H
100
100
66
56
98
62
87
81
100
41
94 (2)
89 (4)
95 (98)
100 (96)
100 (95)
94
95
90 (94)
87
4
7
1
0
0
2[b]
3[b]
CH3
CH3(CH2)2
CH3(CH2)2
H
4[b]
5[c]
6[b]
6
5
7[b]
Cy
Ph
H
Figure 3. Recyclability of the paper catalyst in the hydrogenation of 1-
phenyl-2-propyne-1-ol. Reaction conditions: substrate (1.24 mmol), catalyst
(8 mg, 0.014 mol% Pd), H2 (0.5 MPa), 508C, THF, 2.5 h.
8[c]
CH3CH2
H
H
CH2OH
H
H
10
13
0
10
8
9[c]
(CH2)3OH
PhCHOH
Ph
CH3(CH2)4
CH3(CH2)4
10[c]
11[c,d]
12[b,e]
13[b,f]
100
90
100
100
90 (100)
88 (4)
82 (7)
(Figure 3). Between each reaction, washing with THF was per-
formed prior to the next reaction. Excellent results in terms of
alkene selectivity and conversion were obtained in the five
runs (100% selectivity at 94% of conversion), which thus evi-
dences the robustness of the catalyst under these conditions.
ICP analysis of the organic phase after catalysis confirmed that
no Pd leaching had taken place during these reactions, which
hence demonstrates that the anchoring of Pd@CNT on the
paper is an efficient approach to prepare stable and reusable
catalysts. The stability of the catalyst was attributed to strong
interactions between the metal nanoparticles and the carbon
nanotubes,[7,15] as well as irreversible adsorption of the carbon
nanotubes onto cellulose.[16]
11
[a] Reaction conditions: substrate (1.24 mmol), catalyst (8 mg,
0.014 mol% Pd), THF, quinoline/Pd=104, 1.7ꢁ10À2
quinoline.
[b] 0.3 MPa H2, 308C, 2 h. [c] 0.5 MPa H2, 508C, 2 h. [d] No quinoline was
added. [e] Lindlar catalyst (0.014 mol% Pd). [f] Pd Nanoselect catalyst, LF-
200 (0.014 mol% Pd).
m
selectivity was similar for both substrates (ꢀ95%). For 1-
phenyl-butyne (Table 1, entry 8), 90% selectivity was obtained
at 81% conversion.
In the hydrogenation of the terminal alkynols 4-pentyne-1-ol
and 1-phenyl-2-propyn-1-ol (Table 1, entries 9 and 10), a similar
behavior to that observed for the alkynes was evidenced, as
the alkynol bearing an aromatic ring was converted more
slowly (41 vs. 100%).
In conclusion, a new Pd nanocatalyst supported on paper
was successfully prepared by using multiwalled carbon nano-
tubes as an interface. The catalyst was prepared by decompo-
sition of Pd2(dba)3 under an atmosphere of H2 in the presence
of multiwalled carbon nanotubes and tricyclohexylphosphine
as a stabilizer, followed by their impregnation on paper. This
new nanocatalyst was tested in the semihydrogenation of sev-
eral internal and terminal alkyne and alkynol substrates, and
after optimization of the reaction conditions, excellent selectiv-
ities at high conversions were obtained for all substrates.
Using 1-heptyne as a substrate, similar performances were ob-
tained with commercial catalysts (Lindlar and Pd-Nanoselect
catalysts) under the same conditions. However, recycling of
our paper-based material is more facile, as no filtration is re-
quired. Furthermore, the new catalyst could be recycled five
times without loss of activity or selectivity. This simple and ver-
satile approach is very attractive, as it is easily scalable and
could also be applied to other substrates such as textiles,[17]
plastics,[18] and rubbers.[19]
These results demonstrated that this paper-based catalytic
system could provide excellent selectivity to the alkene prod-
uct at high conversion. For instance, Jung et al. reported the
performance of palladium catalysts supported on carbon nano-
fibers and Pd/activated charcoal in the hydrogenation of 1-
octyne and obtained selectivities towards 1-octene of 68 and
21%, respectively, at 97% of conversion.[14] These values are in-
ferior to those described here using our paper-based catalytic
system. Nikishima et al. reported the hydrogenation of diphe-
nylacetylene by using a polymer/paper-based catalyst but
obtained no selectivity towards the alkene.[4c]
To compare the performance of the paper-based catalyst,
two catalytic reactions were performed by using 1-heptyne as
the substrate in the presence of commercial catalysts (Table 1,
entries 12 and 13), namely, the Lindlar catalyst (5 wt% Pd/
CaCO3, Pb poisoned) and the Pd Nanoselect catalyst (LF-200,
0.5 wt% Pd/TiS). Under these conditions, similar results were
obtained in terms of activity and alkene selectivity for both the
commercial catalysts and the paper-based material reported
herein.
Acknowledgements
The authors would like to acknowledge financial support from
the Spanish Ministry of Science and Innovation (MICINN), the
With these results in hand, the recyclability of the herein-de-
scribed paper-based catalyst was tested in the semihydrogena-
tion of 1-phenyl-2-propyne-1-ol over five consecutive runs
Spanish Ministerio de Economꢀa
y Competividad (Projects
ChemCatChem 2016, 8, 1 – 5
www.chemcatchem.org
3
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
These are not the final page numbers! ÞÞ

Communications
[9] a) M. Novell, M. Parrilla, G. A. Crespo, F. X. Rius, F. J. Andrade, Anal.
Chem. 2012, 84, 4695–4702; b) M. Novell, T. Guinovart, P. Blondeau,
F. X. Rius, F. J. Andrade, Lab on a Chip 2014, 14, 1308–1314.
[10] a) B. Chaudret, C. R. Phys. 2005, 6, 117–131; b) K. Philippot, B. Chaudret,
C. R. Chim. 2003, 6, 1019–1034.
CTQ2013-46404-R and CTQ2013-43438-R), the Ramꢂn y Cajal
Programme, and the Generalitat de Catalunya (2014SGR670).
Keywords: alkynes
·
hydrogenation
·
nanoparticles
·
[11] J. Hori, K. Murata, T. Sugai, H. Shinohara, R. Noyori, N. Arai, N. Kurono, T.
Ohkuma, Adv. Synth. Catal. 2009, 351, 3143–3149.
nanotubes · palladium
[12] J. J. Brunet, P. Caubere, J. Org. Chem. 1984, 49, 4058–4060.
[13] G. Vilꢄ, N. Almora-Barrios, S. Mitchell, N. Lꢅpez, J. Pꢄrez-Ramꢆrez, Chem.
Eur. J. 2014, 20, 5926–5937.
[14] A. Jung, A. Jess, T. Schubert, W. Schꢇtz, Appl. Catal. A 2009, 362, 95–
105.
[1] A. E. Marteel-Parrish, M. A. Abraham in Green Chemistry and Engineering,
Wiley, 2013, pp. 1–19.
[2] C. Descorme, P. Gallezot, C. Geantet, C. George, ChemCatChem 2012, 4,
1897–1906.
[3] M. Crespo-Quesada, F. Cꢂrdenas-Lizana, A.-L. Dessimoz, L. Kiwi-Minsker,
ACS Catal. 2012, 2, 1773–1786.
[15] M. Ruta, N. Semagina, L. Kiwi-Minsker, J. Phys. Chem. C 2008, 112,
13635–13641.
[4] a) K. K. R. Datta, E. Petala, K. J. Datta, J. A. Perman, J. Tucek, P. Bartak, M.
Otyepka, G. Zoppellaro, R. Zboril, Chem. Commun. 2014, 50, 15673–
15676; b) J. W. Lee, T. Mayer-Gall, K. Opwis, C. E. Song, J. S. Gutmann, B.
List, Science 2013, 341, 1225; c) T. Nishikata, H. Tsutsumi, L. Gao, K.
Kojima, K. Chikama, H. Nagashima, Adv. Synth. Catal. 2014, 356, 951–
960; d) G. Zheng, K. Kaefer, S. Mourdikoudis, L. Polavarapu, B. Vaz, S. E.
Cartmell, A. Bouleghlimat, N. J. Buurma, L. Yate, ꢃ. R. de Lera, L. M. Liz-
Marzꢂn, I. Pastoriza-Santos, J. Pꢄrez-Juste, J. Phys. Chem. Lett. 2015, 6,
230–238.
[16] K. Kordꢂs, T. Mustonen, G. Tꢅth, H. Jantunen, M. Lajunen, C. Soldano, S.
Talapatra, S. Kar, R. Vajtai, P. M. Ajayan, Small 2006, 2, 1021–1025.
[17] T. Guinovart, A. J. Bandodkar, J. R. Windmiller, F. J. Andrade, J. Wang, An-
alyst 2013, 138, 7031–7038.
[18] F. X. Rius-Ruiz, D. Bejarano-Nosas, P. Blondeau, J. Riu, F. X. Rius, Anal.
Chem. 2011, 83, 5783–5788.
[19] M. Cuartero, J. S. del Rꢆo, P. Blondeau, J. A. OrtuÇo, F. X. Rius, F. J. An-
drade, Anal. Chim. Acta 2014, 827, 95–102.
[5] P. Serp, M. Corrias, P. Kalck, Appl. Catal. A 2003, 253, 337–358.
[6] a) D. Eder, Chem. Rev. 2010, 110, 1348–1385; b) N. Karousis, N. Tagma-
tarchis, D. Tasis, Chem. Rev. 2010, 110, 5366–5397.
[7] P. Tribolet, L. Kiwi-Minsker, Catal. Today 2005, 105, 337–343.
[8] N. Halonen, A. Rautio, A.-R. Leino, T. Kyllçnen, G. Tꢅth, J. Lappalainen, K.
Kordꢂs, M. Huuhtanen, R. L. Keiski, A. Sꢂpi, M. Szabꢅ, ꢃ. Kukovecz, Z.
Kꢅnya, I. Kiricsi, P. M. Ajayan, R. Vajtai, ACS Nano 2010, 4, 2003–2008.
Received: June 3, 2016
Revised: July 20, 2016
Published online on && &&, 0000
&
ChemCatChem 2016, 8, 1 – 5
www.chemcatchem.org
4
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

COMMUNICATIONS
Plain as paper: A versatile method for
the preparation of efficient and reusable
nanocatalysts involving the painting of
a commercial filter paper with
L. Montiel, J. A. Delgado, M. Novell,
F. J. Andrade, C. Claver, P. Blondeau,*
C. Godard*
&& – &&
a Pd@CNT (CNT=carbon nanotubes)
ink is described. The resulting paper-
based material provides excellent results
in the semihydrogenation of alkynes
and alkynols and can be recycled at
least five times without loss of activity
or selectivity.
A Simple and Versatile Approach for
the Fabrication of Paper-Based
Nanocatalysts: Low Cost, Easy
Handling, and Catalyst Recovery
ChemCatChem 2016, 8, 1 – 5
www.chemcatchem.org
5
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
These are not the final page numbers! ÞÞ