Copper-zinc alloy nanopowder: A robust precious-metal-free catalyst for the conversion of 5-hydroxymethylfurfural

Article abstract of DOI:10.1002/cssc.201403453

Noble-metal-free copper-zinc nanoalloy (<150 nm) is found to be uniquely suited for the highly selective catalytic conversion of 5-hydroxymethylfurfural (HMF) to potential biofuels or chemical building blocks. Clean mixtures of 2,5-dimethylfuran (DMF) and 2,5-dimethyltetrahydrofuran (DMTHF) with combined product yields up to 97 % were obtained at 200-220°C using 20-30 bar H₂. It is also possible to convert 10 wt % HMF solutions in CPME, with an excellent DMF yield of 90 %. Milder temperatures favor selective (95 %) formation of 2,5-furandimethanol (FDM). The one-pot conversion of fructose to valuable furan-ethers was also explored. Recycling experiments for DMF production show remarkable catalyst stability. Transmission electron microscopy (TEM) characterization provides more insight into morphological changes of this intriguing class of materials during catalysis.

Full text of DOI:10.1002/cssc.201403453

DOI: 10.1002/cssc.201403453
Communications
Copper–Zinc Alloy Nanopowder: A Robust Precious-Metal-
Free Catalyst for the Conversion of
5-Hydroxymethylfurfural
Giovanni Bottari,[a] Angela J. Kumalaputri,[b, c] Krzysztof K. Krawczyk,[a] Ben L. Feringa,[a]
Hero J. Heeres,[b] and Katalin Barta*[a]
Noble-metal-free copper–zinc nanoalloy (<150 nm) is found to
be uniquely suited for the highly selective catalytic conversion
of 5-hydroxymethylfurfural (HMF) to potential biofuels or
chemical building blocks. Clean mixtures of 2,5-dimethylfuran
(DMF) and 2,5-dimethyltetrahydrofuran (DMTHF) with com-
bined product yields up to 97% were obtained at 200–2208C
using 20–30 bar H2. It is also possible to convert 10 wt% HMF
solutions in CPME, with an excellent DMF yield of 90%. Milder
temperatures favor selective (95%) formation of 2,5-furandime-
thanol (FDM). The one-pot conversion of fructose to valuable
furan-ethers was also explored. Recycling experiments for DMF
production show remarkable catalyst stability. Transmission
electron microscopy (TEM) characterization provides more in-
sight into morphological changes of this intriguing class of ma-
terials during catalysis.
been developed since,[2,7] including very efficient examples
that use milder temperatures.[8] In contrast, only a few non-pre-
cious-metal-based catalysts have been reported. Recently Fu
and co-workers described a Ni–W carbide catalyst that gave up
to 96% DMF yield.[9] Zhu and co-workers reported on Raney
nickel catalysts with good DMF yields (88.5%) at 1808C.[10]
Despite these promising results, the development of inexpen-
sive, precious metal-free, and highly effective catalysts for this
transformation is still highly desired.
Herein, we report on the use of a robust, sustainable, and
commercially available new catalyst class that allows for modu-
lar and highly selective conversion of HMF to either FDM (up
to 95%) or DMF (up to 90%). Under optimized conditions re-
markably clean mixtures of the two biofuels DMF and DMTHF
(97% yield) can be obtained.
Previously we reported on the use of copper-doped porous
metal oxides[11] in the conversion of HMF and other biomass
The development of new, robust, and efficient catalysts, pri-
marily ones that consist of earth-abundant metals, is of crucial
importance and will enable the sustainable chemical conver-
sion of nonedible lignocellulosic biomass resources[1] or plat-
form molecules derived from such resources.[2] One of the
most versatile platform chemicals is 5-hydroxymethylfurfural
(HMF),[2,3] which can be readily obtained from sugars.[3b] Various
conversion routes have been investigated[4] and among these,
reductive methods are of special importance.[4a] A variety of
new methodologies have been developed for selective carbon-
yl reduction to give 2,5-furan dimethanol (FDM) at milder tem-
peratures.[5] More extensive deoxygenation of HMF to potential
biofuels or the fuel additive 2,5-dimethylfuran (DMF) has been
first proposed by Dumesic.[6a] A number of very efficient cata-
lysts, mainly based on ruthenium[6] or other noble metals, have
resources.[12] Although
a promising combined DMF and
DMTHF[11b] yield of about 80% was obtained, ring-opening pro-
cesses could not be completely prevented owing to the strong
interaction of the relatively basic support with HMF and de-
rived intermediates FDM and MFM (shown in Scheme 1). Thus,
[a] Dr. G. Bottari, Dr. K. K. Krawczyk, Prof. B. L. Feringa, Dr. K. Barta
Stratingh Institute for Chemistry
Scheme 1. Hydrogenation/hydrogenolysis of HMF to DMF and DMTHF mix-
ture (dashed arrows show the simplified pathway involving intermediate
FDM and MFM).
University of Groningen
Nijenborgh 4, 9747 AG Groningen (The Netherlands)
E-mail: k.barta@rug.nl
[b] A. J. Kumalaputri, Prof. H. J. Heeres
Department of Chemical Engineering
University of Groningen
we set out to investigate other suitable classes of copper-con-
taining catalysts, preferably ones that do not readily undergo
deactivation (e.g., by sintering) at elevated temperatures,[13]
and possess a relatively large surface area. We turned our at-
tention to commercially available copper nanopowders, which
are relatively unexplored in catalysis.
Nijenborgh 4, 9747 AG Groningen (The Netherlands)
[c] A. J. Kumalaputri
Department of Chemical Engineering
Parahyangan Catholic University
Ciumbuleuit 94, 40141 Bandung, West Java (Indonesia)
We first screened commercial copper-containing nanopow-
ders of different composition (characterized by elemental anal-
Supporting Information for this article is available on the WWW under
http://dx.doi.org/10.1002/cssc.201403453.
ChemSusChem 0000, 00, 0 – 0
1
ꢀ 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
These are not the final page numbers! ÞÞ

Communications
Figure 1. Comparison of the product distribution (GC selectivities) obtained
in the HMF hydrodeoxygenation over different copper nanopowders. Condi-
tions: 0.500 g HMF, 0.100 g copper nanopowder, EtOH (20 mL), 2208C,
30 bar H2, 6 h (n.i: not identified; r.o.: ring-opening products). The corre-
sponding numerical values are displayed in table S2.
Figure 2. Effect of different solvents for DMF+DMTHF production (0.500 g
HMF, 0.100 g CuZn, 2208C, 18 h, 20 bar H2). On the right, the 10 wt% HMF
experiment was conducted in CPME (1.72 g HMF, 0.2 g CuZn, 2008C, 6 h,
20 bar H2).
ysis and XRD, see Supporting Information, Table S1 and Fig-
ure S1) in the conversion of HMF to DMF (Scheme 1). All reac-
tions were carried out in ethanol at 2208C using 30 bar H2
pressure for 6 h (Figure 1; Supporting Information, Table S2).
Complete or nearly complete (95% with CuZnFe2O4) conver-
sion of HMF was achieved with all tested nanopowders, but
variations in the composition of the obtained product mixtures
were significant. Copper nanopowder showed a good (55%)
DMF+DMTHF yield, with a DMF/DMTHF ratio of 20:1. Ether 2-
(ethoxymethyl)-5-methylfuran (EMMF) was found as a main re-
action product, and a small amount of ring-opening and hy-
drogenation products were also seen.
metal oxides.[11b] Indeed, with iPrOH and methyl isobutyl carbi-
nol (MIBC) excellent product yields were obtained (91% and
93% respectively). No corresponding etherification products
were observed with bulkier alcohols. The quantity of unidenti-
fied compounds was below 3%. Interestingly, the DMF/DMTHF
ratio reduced from 14:1 in EtOH to 4:1 in MIBC (Figure 2).
Ethereal solvents such as 2-MeTHF (2-methyltetrahydrofuran)
and CPME (cyclopentyl methyl ether) were also tested. 2-
MeTHF, which is directly accessible from renewable resour-
ces,[14] performed comparably high to MIBC and iPrOH. To our
delight CPME, a favorable solvent with low toxicity and negligi-
ble peroxide formation[15] afforded the highest DMF+DMTHF
yield (97%; see Supporting Information, Figure S8 for the cor-
responding GC trace). This practically means that upon HMF
conversion under these conditions, analytically pure fuel mix-
tures were obtained.
In this run many smaller peaks were also detected, which ac-
counted for about 20% of unidentified products, likely caused
by the relatively high loading of copper (20 wt%). As a compar-
ison, with CuO a low DMF yield was found, and the biggest
fraction of the product mixture (50%) consisted of FDM and
MFM, indicating an overall slower reaction. Similarly, mixed
copper-iron oxide nanopowder led to only 45% product.
CuZnFe2O4 of similar composition performed better (73%
product yield), however 12% of the products still remained un-
identified. Best among the tested catalyst was the CuZn nano-
alloy, which afforded 75% DMF+DMTHF yield with a DMF/
DMTHF ratio of 14:1, while the two main “precursors” to DMF
(FDM and MFM) still represented 13% of the product mixture
after 6 h reaction time. Overall, the cleanest product mixtures
were obtained with this catalyst since only 3% of the products
were unidentified.
In both these solvents, the DMF/DMTHF ratio was lower
than in ethanol. Figure 2 shows an overview of the increase of
the overall DMF+DMTHF yield from ethanol to CPME; howev-
er, at the expense of the DMF/DMTHF ratio.
The reaction conditions were further optimized in CPME.
The reaction time could be reduced to 3 h at 2008C with no
apparent change in product yield, but increase in DMF content
(Table 1, entries 1–3). To our delight, even concentrated HMF
Table 1. DMF+DMTHF production in CPME solvent.
Entry[a]
t
[h]
T
[8C]
DMF+DMTHF
yield [%][b]
DMF/DMTHF
ratio[b]
Thus CuZn nanopowder was selected for further studies
(Supporting Information, Table S3). First, the reaction time was
prolonged to 18 h to ensure a full conversion of intermediates
(FDM and MFM). Indeed, the product yield improved from
75% to 83%. Adjusting the H2 pressure allowed for a further
small increase to a very good, 88% product yield. The solvent
engaged to a small extent in side reactions, as evidenced by
the formation of 5% EMMF (Table S3 and Supporting Informa-
tion, Scheme S1). To minimize these side processes and im-
prove product yields even further, bulkier alcohol solvents
were screened, as was earlier reported with copper porous
1
2
3
4[c]
5[d]
6
6
3
6
18
220
200
200
200
220
97
97
96
94
89
3:1
5:1
5:1
18:1
35:1
[a] Reaction conditions: 0.500 g HMF, 0.100 g CuZn, 20 mL CPME,
0.250 mL decane, 20 bar H2. Full HMF conversion. [b] Determined by GC-
FID. [c] 10 wt% HMF concentration (1.72 g HMF in 20 mL CPME) and
0.2 g catalyst were used (7% Cu/HMF ratio). [d] 2.00 g HMF in 30 mL
CPME, 40 bar H2, and 0.1 g catalyst were used (3% Cu/HMF ratio).
&
ChemSusChem 0000, 00, 0 – 0
www.chemsuschem.org
2
ꢀ 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Communications
solutions (10 wt%) were cleanly converted into a mixture of
DMF and DTMHF (94% yield; entry 4 and Figure 2) in CPME,
while DMF yield was 90%. Similarly a 10 wt% HMF solution
was converted in MIBC at 2208C and longer reaction time,
albeit with slightly lower DMF+DMTHF yield (88%). Interest-
ingly, a 5 w% catalyst loading (3 w% Cu), typical for noble
metal catalysts was adopted in CPME solvent with full sub-
strate conversion, 89% combined fuel yield, and excellent
DMF/DMTHF ratio of 35:1. This holds much promise for future
upscaling, and continuous operation of this system.
In the bulk, core–shell structures in which the zinc is cover-
ing highly copper-dense particles were observed. These mor-
phological changes in the alloy structure are probably due to
copper migration, which becomes relevant above 2008C.[17]
Despite these variances, only a slight difference between the
bulk composition of the spent catalyst (MIBC) and the fresh
catalyst could be determined by ICP analysis (Supporting Infor-
mation, Table S7), showing practically no metal loss into the
solution. In addition, combustion analysis detected an elevated
carbon content (0.6%; Supporting Information, Table S7) in the
spent catalyst (MIBC), and accordingly thermogravimetric anal-
In addition, 5-(ethoxymethyl)furfural (EMF) was used as start-
ing material instead of HMF in CPME (2208C, 18 h, 20 bar H2).
This ether also underwent hydrogenolysis, resulting in good
DMF+DMTHF yield (78%). The corresponding EMMF, a poten-
tial fuel additive was detected as second major product (10%).
This is promising regarding possible DMF production directly
from hexoses, through HMF ethers.[16]
ysis (Supporting Information, Figure S2) showed
a slight
(<2%) decrease in weight between 1008C and 4008C, which
can be attributed to adsorbed organics.
Recycling experiments were successfully performed in both
these solvents, with better performance in CPME. Experiments
in MIBC were carried out with 0.5 g HMF and 0.2 g CuZn at
2208C for 15 h (Supporting Information, Figure S7 and
Table S9). Interestingly, with decreasing activity, the DMF/
DMTHF ratio increased up to 30:1, the 2nd cycle representing
an almost perfect DMF selectivity. After the 2nd cycle, the prod-
uct yield gradually decreased from ca. 90% (1–2nd cycle) to
17% (4th cycle). Notably, calcination of the spent catalyst after
the 4th run at 5008C for 6 h recovered the catalytic activity and
even the DMF/DMTHF ratio in the 5th run was precisely identi-
cal to the initial value. Accordingly, TEM analysis of the catalyst
recovered after the 4th run showed core–shell structures (Sup-
porting Information, Figure S6), not present in the original
solid; this morphological change together with the presence
of organics adsorbed on the catalyst surface might be the
cause of deactivation. After calcination, the morphology of the
catalyst (Figure S6) displays a substantial regeneration of the
original alloy structure. The transition from a core–shell struc-
ture into an homogeneous alloy has already been reported.[18]
The catalyst has proven even more stable in CPME (Support-
ing Information, Figure S7 and Table S10). Recycling tests in
CPME were performed at 2208C using 0.5 g HMF and 0.2 g
CuZn nanoalloy. No relevant loss in catalytic activity was ob-
served in the first 5 cycles (ca. 90%), then the DMF+DMTHF
yield decreased to 66% after the 6th cycle, and 3% product
yield was observed in the 7th cycle, corresponding to a total of
3.5 g HMF converted. At this point, calcination was performed
and the initial activity regained. From the above experiments it
can be concluded that CuZn is a robust and highly active cata-
lyst for the conversion of HMF to DMF, suitable for continuous-
flow setup.
The catalyst residues from the 10 wt% runs in CPME and
MIBC were recovered and analyzed by transmission electron
microscopy (TEM), and compared with the fresh catalyst (Sup-
porting Information, Figure S4). The spent catalyst recovered
from the run in CPME (Table 1, entry 4) mainly showed ag-
glomerated particles with a core–shell structure. However, after
reaction in MIBC (Table S3, entry 7), spike-shaped objects were
visible on the catalyst surface in addition to coagulated round-
ed particles, also present in the fresh catalyst. For further direct
morphological comparison, the reaction was also carried out in
CPME using the same experimental conditions as in MIBC
(10 wt% HMF, 2208C, 18 h). No spiked objects were detected
and cleaner product mixtures and higher DMF+DMTHF yields
were observed in CPME. This shows that changes in catalyst
morphology are dependent on the nature of the solvent and
might influence catalytic activity.
The local composition of the spiked nanostructures was de-
termined by energy dispersive X-ray (EDX) analysis, which re-
vealed that these mostly comprise zinc (>90%) as highlighted
by elemental analysis and lattice constant value (Figure 3 and
Supporting Information, Figure S5).
The specific roles of the copper and zinc metals in catalysis,
or their oxides, which might also be present in smaller
amounts, has yet to be elucidated. Recent photoelectron spec-
troscopy studies reported the formation of zinc oxide islands
on particle surface in CuZn nanoalloys.[19] The presence of the
ZnO phase was confirmed during XRD analysis of the CuZn
nanopowder (Figure S1). The beneficial effect on DMF produc-
tion of acidic Zn2+ sites contained in Pd/Zn/C catalysts was re-
cently proposed by Abu Omar et al.[20] It seems plausible that
active Cu0 species are responsible for hydrogenation/hydroge-
nolysis with the assistance of Lewis-acidic ZnO sites. Similar
Figure 3. TEM image of spent catalyst after the run at 10wt% HMF concen-
tration in MIBC (Table S3, entry 7). In the insert, a magnification of a spiked-
like object and the corresponding elemental mapping by EDX are provided.
ChemSusChem 0000, 00, 0 – 0
www.chemsuschem.org
3
ꢀ 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
These are not the final page numbers! ÞÞ

Communications
synergistic effects were observed in a recent catalytic applica-
tion.[21] Cooperative effect in bimetallic noble metal catalysts
designed for HMF to DMF conversion has been recently report-
ed.[22]
Particle size is a crucial parameter, and determining ideal
size ranges is essential for catalytic application of “bras-
ses”.[5d,23,27] We have briefly addressed this point by comparing
the catalytic activity of commercially available CuZn alloys of
various sizes. Indeed, CuZn alloys with 25–250 mm and
<25 mm particle size showed low activity at 2208C for 6 h in
EtOH, thus it appears that the <150 nm size is crucial. For
future studies, several procedures for the synthesis of different
nanosized CuZn structures with a bottom-up approach are
available.[23]
Scheme 3. One-pot and two-step strategies for the valorization of fructose
in iPrOH.
tion were moderately successful. 1, 2, and 3 were obtained in
modest yields (20% in both cases, Table S12) when a mixture
of 4 and 5 obtained by dehydration with Nafion SAC-13 and
Amberlyst 15 were hydrogenated using 1208C and 30 bar H2.
Interestingly, the corresponding one-pot process starting di-
rectly from fructose with CuZn catalyst and Nafion SAC-13 or
Amberlyst 15 (Supporting Information, Table S13) was more
successful. In this case, fructose conversion was 96% using
Nafion SAC-13 and 1 and 2 were found as only products in 1%
and 33% yields, respectively. With Amberlyst 15, a good com-
bined 50% yield of 1 and 2 was observed at full fructose con-
version, in addition 7% FDM was detected. These results com-
pare well with the yields found in the literature using noble
metal catalysts.[26]
Another important aspect, using the commercially obtained
CuZn nanopowder, is the reproducibility of results regarding
batch to batch variations. No significant variation (within 6%)
in DMF selectivities was observed when using four different
batches from two different suppliers (Supporting Information,
Table S8).
Next, the copper zinc nanopowder was tested in the hydro-
genation of HMF at mild temperature to provide useful diol
building blocks (Scheme 2). It is known that a,w-diols, for ex-
In conclusion, a noble-metal-free copper–zinc nanoalloy is
applied for the first time in the highly selective hydrodeoxyge-
nation of HMF to biofuels (up to 97% DMF+DMTHF yield)
and diol building blocks (up to 95% FDM). Alloys play a crucial
role in heterogeneous catalysis, however, ‘nanobrasses’ are not
yet explored in catalysis.[5d,27] Recent reports identify CuZn
alloys as promising systems for methanol[23a] and dimethylether
synthesis.[21] Based on these studies and the results reported in
this paper, we foresee a more general use of “nanobrasses” in
the conversion of renewable resources in the future.
Scheme 2. Selective formation of useful diol building blocks from HMF.
ample, 1,6-hexanediol are important polymer precursors.[24]
A screening of various commercial catalysts was carried out in
ethanol at 1208C for 3 h (for details see Supporting Informa-
tion, page 5 and Tables S5–S6). All catalysts preferentially af-
forded either THFDM (2,5-tetrahydrofurandimethanol) or FDM
(2,5-furandimethanol), depending on compositions. The best
FDM selectivity (95%; Supporting Information, Figure S9 for
GC trace) was achieved with the CuZn nanoalloy while >99%
THFDM, was obtained over Pd/Al2O3 as a mixture of cis and
trans isomer in 9:1 ratio (Supporting Information, Table S5,
entry 7; Figures S10–S12).
Experimental Section
General procedure for hydrogenation reactions: In a typical ex-
periment,
a glass insert containing 5-(hydroxymethyl)furfural
(0.500 g), the catalyst (0.100 g) and toluene or decane (0.250 mL,
internal standard) in the appropriate solvent (20 mL) was placed in
a 100 mL stainless-steel Parr reactor. After purging 3 times with H2,
the reactor was pressurized at the desired pressure, heated, and
stirred with a mechanical stirrer (600 rpm). After reaction, the reac-
tor was cooled down to room temperature and the mixture was fil-
tered and injected into a GC-MS-FID to determine conversion,
product selectivity, and yield (by internal standard method). For
characterization of the spent catalyst, the reaction mixture was
centrifuged and the solid was washed two additional times with
acetone and dried at 1108C for 6 h. Recycling experiments are de-
scribed in detail in the Supporting Information.
Given the excellent performance of the CuZn nanoalloy in
FDM formation, we next attempted the more challenging one-
pot dehydration/hydrogenation reaction starting directly from
fructose. An elegant approach for obtaining HMF and its
ethers from fructose in isopropanol solvent has recently been
reported.[25] First, fructose dehydration was conducted at
1208C in iPrOH using different acid resins. HMF (4) and the cor-
responding isopropyl ether (5) were the main products, their
ratio being dependent on the type of acidic catalyst used
(Scheme 3; Supporting Information, Table S11). Amberlyst 15
and Nafion SAC-13 preferentially afforded HMF while with
Dowex 50WX8 resin ether, 5 was found as main product.
Attempts to hydrogenate the crude mixtures with CuZn
nanopowder after removal of the acidic resin by simple filtra-
Acknowledgements
The authors acknowledge support from the European Commis-
sion’s Framework Programme 7, through the Marie Curie IEF
scheme. We are also grateful to Dr. Marc Stuart for the TEM and
EDX measurements.
&
ChemSusChem 0000, 00, 0 – 0
www.chemsuschem.org
4
ꢀ 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Communications
[12] K. Barta, P. C. Ford, Acc. Chem. Res. 2014, 47, 1503–1512.
[13] B. J. O’Neill, et al., Angew. Chem. Int. Ed. 2013, 52, 13808–13812; Angew.
Chem. 2013, 125, 14053–14057.
Keywords: 5-(hydroxymethyl)furfural · biomass · copper ·
hydrogenolysis · zinc
[14] a) H. Mehdi, V. Fꢂbos, R. Tuba, A. Bodor, L. T. Mika, I. T. Horvꢂth, Top.
Catal. 2008, 48, 49–54; b) F. M. A. Geilen, B. Engendahl, A. Harwardt, W.
Marquardt, J. Klankermayer, W. Leitner, Angew. Chem. Int. Ed. 2010, 49,
5510–5514; Angew. Chem. 2010, 122, 5642–5646; c) V. Pace, P. Hoyos,
L. Castoldi, P. Domꢃnguez de Marꢃa, A. R. Alcꢂntara, ChemSusChem 2012,
5, 1369–1379.
[1] a) M. Sankar, N. Dimitratos, P. J. Miedziak, P. P. Wells, C. J. Kiely, G. J.
Hutchings, Chem. Soc. Rev. 2012, 41, 8099–8139; b) C. O. Tuck, E. Pꢁrez,
I. T. Horvꢂth, R. A. Sheldon, M. Poliakoff, Science 2012, 337, 695–699;
c) Catalysis for Renewables (Eds.: G. Centi, R. A. van Santen), Wiley-VCH,
Weinheim, 2007.
[15] a) K. Watanabe, N. Yamagiwa, Y. Torisawa, Org. Process Res. Dev. 2007,
11, 251–258; K. Watanabe, Molecules 2013, 18, 3183–3194.
[16] a) C. M. Lew, N. Rajabbeigi, M. Tsapatsis, Ind. Eng. Chem. Res. 2012, 51,
5364–5366; b) L. Bing, Z. Zhang, K. Deng, Ind. Eng. Chem. Res. 2012, 51,
15331–15336; c) Z. Zhang, Y. Wang, Z. Fang, B. Liu, ChemPlusChem
2014, 79, 233–240; d) B. Liu, Z. Zhang, RSC Adv. 2013, 3, 12313–12319.
[17] M. V. Twigg, M. S. Spencer, Appl. Catal. A 2001, 212, 161–174.
[18] a) A. R. Wilson, K. Sun, M. Chi, R. M. White, J. M. LeBeau, H. H. Lamb, B. J.
Wiley, J. Phys. Chem. C 2013, 117, 17557–17566; b) L. Arroyo-Ramꢃrez, C.
Chena, M. Cargnello, C. B. Murray, P. Fornasiero, R. J. Gorte, J. Mater.
Chem. A 2014, 2, 19509–19514.
[2] a) C. Chatterjee, F. Pong, A. Sen, Green Chem. 2015, 17, 40–71; b) J. J.
Bozell, G. R. Petersen, Green Chem. 2010, 12, 539–554; c) M. Besson, P.
Gallezot, C. Pinel, Chem. Rev. 2014, 114, 1827–1870.
[3] a) R.-J. van Putten, J. C. van der Waal, E. de Jong, C. B. Rasrendra, H. J.
Heeres, J. G. de Vries, Chem. Rev. 2013, 113, 1499–1597; b) B. Saha,
M. M. Abu-Omar, Green Chem. 2014, 16, 24–38.
[4] a) Y. Nakagawa, M. Tamura, K. Tomishige, ACS Catal. 2013, 3, 2655–
2668; b) O. O. James, S. Maity, L. Ajao Usman, K. O. Ajanaku, O. O. Ajani,
T. O. Siyanbola, S. Sahuc, R. Chaubey, Energy Environ. Sci. 2010, 3, 1833–
1850; c) F. M. A. Geilen, T. vom Stein, B. Engendahl, S. Winterle, M. A.
Liauw, J. Klankermayer, W. Leitner, Angew. Chem. Int. Ed. 2011, 50,
6831–6834; Angew. Chem. 2011, 123, 6963–6966; d) A. D. Sutton, F. D.
Waldie, R. Wu, M. Schlaf, L. A. Silks, J. C. Gordon, Nat. Chem. 2013, 5,
428–432; e) I. Sꢂdaba, Y. Y. Gorbanev, S. Kegnaes, S. Sankar, R. Putluru,
R. W. Berg, A. Riisager, ChemCatChem 2013, 5, 284–293.
[19] K. Ozawa, Y. Mimori, H. Kato, S. Imanishi, K. Edamoto, K. Mase, Surf. Sci.
2014, 623, 1–5.
[20] B. Saha, C. M. Bohn, M. M. Abu-Omar, ChemSusChem 2014, 7, 3095–
3101.
[21] J. Sun, G. Yang, Q. Ma, I. Ooki, A. Taguchi, T. Abe, Q. Xie, Y. Yoneyama, N.
Tsubaki, J. Mater. Chem. A 2014, 2, 8637–8643.
[5] a) M. Chatterjee, T. Ishizaka, H. Kawanami, Green Chem. 2014, 16, 4734–
4739; b) M. Tamura, K. Tokonami, Y. Nakagawa, K. Tomishige, Chem.
Commun. 2013, 49, 7034–7036; c) J. Ohyama, A. Esaki, Y. Yamamoto, S.
Arai, A. Satsuma, RSC Adv. 2013, 3, 1033–1036; d) R. Alamillo, M. Tucker,
M. Chia, Y. Pagꢂn-Torres, J. Dumesic, Green Chem. 2012, 14, 1413–1419;
e) T. Thananatthanachon, T. Rauchfuss, ChemSusChem 2010, 3, 1139–
1141.
[6] a) Y. Romꢂn-Leshkov, C. J. Barrett, Z. Y. Liu, J. A. Dumesic, Nature 2007,
447, 982–986; b) L. Hu, X. Tang, J. Xu, Z. Wu, L. Lin, S. Liu, Ind. Eng.
Chem. Res. 2014, 53, 8, 3056–3064; c) J. Jae, W. Zheng, A. M. Karim, W.
Guo, R. F. Lobo, D. G. Vlachos, ChemCatChem 2014, 6, 848–856; d) Y.
Zu, P. Yang, J. Wang, X. Liu, J. Ren, G. Lu, Y. Wang, Appl. Catal. B 2014,
146, 244–248; e) J. Jae, W. Zheng, R. F. Lobo, D. G. Vlachos, ChemSu-
sChem 2013, 6, 1158–1162; f) J. B. Binder, R. T. Raines, J. Am. Chem. Soc.
2009, 131, 1979–1985.
[22] G.-H. Wang, J. Hilgert, F. H. Richter, F. Wang, H.-J. Bongard, B. Spliethoff,
C. Weidenthaler, F. Schꢄth, Nat. Mater. 2014, 13, 293–300.
[23] a) K. Schꢄtte, H. Meyer, C. Gemel, J. Barthel, R. A. Fischer, C. Janiak,
Nanoscale 2014, 6, 3116–3126; b) M. Cokoja, H. Parala, M. K. Schroeter,
A. Birkner, M. W. van den Berg, K. V. Klementiev, W. Gruenert, R. A. Fisch-
er, J. Mater. Chem. 2006, 16, 2420–2428.
[24] a) J. Tuteja, H. Choudhary, S. Nishimura, K. Ebitani, ChemSusChem 2014,
7, 96–100; b) T. Buntara, S. Noel, P. Huat Phua, I. Meliꢂn-Cabrera, J. G.
de Vries, H. J. Heeres, Top. Catal. 2012, 55, 612–619; c) T. Buntara, S.
Noel, P. Huat Phua, I. Meliꢂn-Cabrera, J. G. de Vries, H. J. Heeres, Angew.
Chem. Int. Ed. 2011, 50, 7083–7087; Angew. Chem. 2011, 123, 7221–
7225.
[25] L. Lai, Y. Zhang, ChemSusChem 2011, 4, 1745–1748.
[26] a) M. Balakrishnan, E. R. Sacia, A. T. Bell, Green Chem. 2012, 14, 1626–
1634.
[27] a) S. Zafeiratos, S. Piccinin, D. Teschner, Catal. Sci. Technol. 2012, 2,
1787–1801; b) R. Ferrando, J. Jellinek, R. L. Johnston, Chem. Rev. 2008,
108, 845–910.
[7] a) S. Nishimura, N. Ikeda, K. Ebitani, Catal. Today 2014, 232, 89–98; b) D.
Scholz, C. Aellig, I. Hermans, ChemSusChem 2014, 7, 268–275.
[8] a) J. Mitra, X. Zhou, T. Rauchfuss, Green Chem. 2015, 17, 307–313; b) M.
Chatterjee, T. Ishizaka, H. Kawanami, Green Chem. 2014, 16, 1543–1551.
[9] Y.-B. Huang, M.-Y. Chen, L. Yan, Q.-X. Guo, Y. Fu, ChemSusChem 2014, 7,
1068–1070.
[10] X. Kong, Y. Zhu, H. Zheng, F. Dong, Y. Zhu, Y.-W. Li, RSC Adv. 2014, 4,
60467–60472.
[11] a) T. S. Hansen, K. Barta, P. T. Anastas, P. C. Ford, A. Riisager, Green Chem.
2012, 14, 2457–2461; b) A. Kumalaputri, G. Bottari, P. M. Erne, H. J.
Heeres, K. Barta, ChemSusChem 2014, 7, 2266–2275.
Received: December 23, 2014
Published online on && &&, 0000
ChemSusChem 0000, 00, 0 – 0
www.chemsuschem.org
5
ꢀ 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
These are not the final page numbers! ÞÞ

COMMUNICATIONS
G. Bottari, A. J. Kumalaputri,
K. K. Krawczyk, B. L. Feringa, H. J. Heeres,
K. Barta*
&& – &&
Revival of the ‘brass-age’: Commercial-
ly available copper–zinc nanopowder
proves very robust and highly effective
in the reduction of HMF to either fuel
additives or useful chemical building
blocks. Fuel yields of up to 97% and
FDM yield up to 95% were obtained.
The one-pot conversion of fructose to
furanic diethers is also achieved, in iso-
propanol solvent.
Copper–Zinc Alloy Nanopowder: A
Robust Precious-Metal-Free Catalyst
for the Conversion of
5-Hydroxymethylfurfural
&
ChemSusChem 0000, 00, 0 – 0
www.chemsuschem.org
6
ꢀ 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!