Isolated Fe(III)-O Sites Catalyze the Hydrogenation of Acetylene in Ethylene Flows under Front-End Industrial Conditions

Article abstract of DOI:10.1021/jacs.8b04669

The search for simple, earth-abundant, cheap, and nontoxic metal catalysts able to perform industrial hydrogenations is a topic of interest, transversal to many catalytic processes. Here, we show that isolated Fe^III-O sites on solids are able to dissociate and chemoselectively transfer H₂ to acetylene in an industrial process. For that, a novel, robust, and highly crystalline metal-organic framework (MOF), embedding Fe^III-OH₂ single sites within its pores, was prepared in multigram scale and used as an efficient catalyst for the hydrogenation of 1% acetylene in ethylene streams under front-end conditions. Cutting-edge X-ray crystallography allowed the resolution of the crystal structure and snapshotted the single-atom nature of the catalytic Fe^III-O site. Translation of the active site concept to even more robust and inexpensive titania and zirconia supports enabled the industrially relevant hydrogenation of acetylene with similar activity to the Pd-catalyzed process.

Full text of DOI:10.1021/jacs.8b04669

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Article
Isolated Fe(III)–O Sites Catalyze the Hydrogenation of Acetylene
in Ethylene Flows under Front–End Industrial Conditions
María Tejeda-Serrano, Marta Mon, Bethany Ross, Francisco Gonell, Jesus Ferrando-
Soria, Avelino Corma, Antonio Leyva-Perez, Donatella Armentano, and Emilio Pardo
J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.8b04669 • Publication Date (Web): 25 Jun 2018
Downloaded from http://pubs.acs.org on June 25, 2018
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Isolated Fe(III)–O Sites Catalyze the Hydrogenation of Acetylene in
Ethylene Flows under Front–End Industrial Conditions
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‡,◊
†,◊
‡
‡
María Tejeda–Serrano, Marta Mon, Bethany Ross, Francisco Gonell, Jesús Ferrando–
†
,‡
,‡
,§
,†
Soria, Avelino Corma,* Antonio Leyva–Pérez,* Donatella Armentano* and Emilio Pardo*
†
Instituto de Ciencia Molecular (ICMol), Universidad de Valencia, 46980 Paterna, Valencia, Spain
‡
Instituto de Tecnología Química (UPV–CSIC), Universitat Politècnica de València–Consejo Superior de Investiga-
ciones Científicas, Avda. de los Naranjos s/n, 46022 Valencia, Spain
§
Dipartimento di Chimica e Tecnologie Chimiche (CTC), Università della Calabria, Rende 87036, Cosenza, Italy
◊These authors equally contributed to the work.
ABSTRACT: The search for simple, earth–abundant, cheap and non–toxic metal catalysts able to perform industrial hy-
III
drogenations is a topic of interest, transversal to many catalytic processes. Here, we show that isolated Fe –O sites on
solids are able to dissociate and chemoselectively transfer H to acetylene in an industrial process. For that, a novel, ro-
2
III
bust and highly crystalline Metal–Organic Framework (MOF), embedding Fe –OH single–sites within its pores, was
2
prepared in multigram–scale and used as an efficient catalyst for the hydrogenation of 1% acetylene in ethylene streams
under front–end conditions. Cutting–edge X–ray crystallography allowed the resolution of the crystal structure and snap-
III
shotted the single–atom nature of the catalytic Fe –O site. Translation of the active site concept to even more robust and
inexpensive titania and zirconia supports enabled the industrially relevant hydrogenation of acetylene with similar activi-
ty to Pd–catalyzed process.
makes them suitable candidates for gas–phase catalysis.
INTRODUCTION
MOFs’ catalysis can be originated either from open metal
II
13
Nature uses Fe –containing hydrogenase enzymes to
sites of the coordination network, or –by taking ad-
1
14–18
activate and transfer H , and following this concept,
chemists have designed organometallic Fe complexes
able to catalyze the hydrogenation of unsaturated carbon
bonds in organic molecules. More available and robust
vantage of the rich host–guest chemistry
of these po-
2
II
rous materials– from active guest species judiciously
19–23
placed in the pores.
Indeed, MOFs are especially good
2
23
24
for supporting metal cations, complexes or small clus-
III
19,25
forms of Fe, such as Fe oxides, may also dissociate and
ters
anchoring them to the walls of their channels. As a
transfer H to simpler but industrially relevant substrates,
result, MOFs can exhibit extremely high catalytic activi-
ties –often combined with size–selectivity related to such
confined state– exceptional characterization of the guest
active species –by means of single crystal X–ray diffrac-
2
3
,4
i.e. acetylene, if the catalytic site is suitably designed. If
III
so, industrial hydrogenations with convenient Fe solid
catalysts could be carried out.
26,27
tion–
to metal catalysts in solution.
The preparation of MOFs has been, traditionally, con-
and also improved reuse capabilities compared
Polyethylene accounts for nearly 30% of the total pro-
duction of plastics worldwide, which reaches more than
1
9
3
00 million tons every year. Prior to polymerization, the
28
selective hydrogenation of the remnant acetylene (ca. 1%)
in the raw ethylene stream is necessary, otherwise the
polymerization catalyst is poisoned or explosive acetylides
can be formed. Traditionally, the hydrogenation of acety-
lene has been mostly catalyzed by noble metals –
including supported noble–metal nanocatalysts– such as
nected with the use of direct self–assembly methods.
However, very recently, a new synthetic avenue has
emerged for the fabrication of functional MOFs. This is
29–33
the so–called post–synthetic (PS) methodology,
con-
sisting firstly on the selection of preformed MOFs and
3
4,35
secondly, on the solid–state incorporation
of the de-
5
Pd, Pt or Ru. Aiming at reducing the ecological footprint
sired functional species within the channels of the MOF.
associated to the use of such scarce metals in multi–ton
industrial processes, further efforts are required to devel-
op novel catalysts based on more abundant and less ex-
RESULTS AND DISCUSSION
On this basis, in this work Ni(II) cations hosted in the
hydrophilic octagonal pores of a highly crystalline MOF,
6–9
pensive metals such as transition ones.
1
0
II
II
II
31
Metal–organic frameworks (MOFs) –a highly versatile
type of crystalline porous materials– have shown excellent
of formula Ni {Ni [Cu (Me mpba) ] } · 54H O (1)
2
4
2
3
2 3
2
4
–
[where Me mpba
is the N,N’–2,4,6–trimethyl–1,3–
3
1
1
12
results in both gas adsorption and catalysis, which
phenylenebis(oxamate) ligand (Scheme 1)], were single–
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III
III
2
crystal to single–crystal (SC to SC) solid–state PS ex-
changed by Fe cations, supported and stabilized within
compound
of
formula
[Fe (H O) ][Fe (µ–
2
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II
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O) (H O) ] {Ni [Cu (Me mpba) ] } · 72H O (2) (Figure
2
2
6 1/2
4
2
3
2 3
2
MOF channels by anchoring them to the walls of the net
(Figures 1 and S1–S7). This PS exchange yielded the novel
S1).
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Figure 1. Views of the porous crystal structures, determined by single crystal X–ray diffraction, of 2 along the c (left) and a
(right) axes, respectively. (b) Perspective views of the porous crystal structures of one single channel of 2 along the c (left) and a
(
right) axes, respectively. Copper(II) and nickel(II) cations from the coordination network are represented by cyan and blue
polyhedra, respectively, whereas the ligands are depicted as gray sticks. Iron(III) cations and water molecules hosted in the
channels are represented by gold and red spheres with surface, respectively. Dotted lines represent the hydrogen bonds between
the network and the iron units.
II
III
The replacement of Ni cations by Fe ones, simply
soaking crystals of 1 in an aqueous solution of ammonium
iron(II) sulfate during one week in open air (see Experi-
mental Section, Supporting Information), was monitored
through SEM–EDX and ICP–AES, whereas Fe oxidation
state was determined by X–ray photoelectron spectrosco-
py (XPS, Figure S8a).
After the PS cation exchange, the crystal structure of
the new compound 2 unambiguously shows [Fe (H O) ]
III
3+
2
6
III
2+
and [Fe2 (µ–O) (H O) ] units, confined and retained in
the larger accessible hydrophilic octagonal channels and
the small hindered square ones, respectively (Figures 1
and S3–S7). Either penta–coordinated Fe ions from the
centrosymmetric dinuclear entities (Figure S4) or the rare
hexa–aqua monomers exhibit Fe–O and Fe–OH bond
2
2
6
III
2
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distances [1.99(1)–2.22(1) Å] in the range of those found in Figure 2 shows the hydrogenation of acetylene (1.2%) in
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2
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the literature.
an ethylene flow (1 ml/min, 2 bar) catalyzed by MOF 2 (25
mg) in a fixed–bed reactor, with an excess of H2 (2
ml/min, 4 bar) at 150 °C, and with a gas hourly space
The larger accessible void space of the octagonal chan-
nels (ca. 2.2 nm), contrasting with the very limited acces-
sible space of the smaller ones (Figure 1), suggests that
–1
velocity (GHSV) of 4000 h , which are simulating condi-
3
7
III
3+
tions of real industrial front–end parameters. The results
show that acetylene is hydrogenated to less than 10 ppm
(instrumental detection limit) and ethane formation is
initially below 10%, which are typical values for some Pd
[
Fe (H O) ] monomers are prominent catalytic species
2 6
(vide infra). The intrinsic capability of water in embroider-
ing infinite H–bonding grids ensures fixation and stabili-
zation of both units in the pores by strong interactions,
involving the oxygen atoms of the pore walls from ox-
3
8
industrial catalysts. However, after some time, ethane
production steadily increases, which indicates that the
MOF catalyst is evolving and losing selectivity under
reaction conditions with time. Lower temperatures do not
achieve the full hydrogenation of acetylene (Figure S13).
In any case, this result represents a step forward on MOFs
catalysis. In fact, it is difficult to find in the literature any
MOF able to catalyze a continuous process, under simu-
III
1
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amate ligands and water molecules surrounding Fe ions
[Owaters···Ooxamate 2.89 and 2.85 Å, for monomers and di-
mers, respectively] (Figures 1, S2, S6 and S7). The highly
hydrated and largely accessible MOF’s nano–confined
space represents a unique and powerful tool to safeguard
catalytic species, both stabilizing and triggering them on
demand.
1
9,39,40
lating industrial conditions.
The experimental powder X–ray diffraction (PXRD)
patterns of a polycrystalline sample of 2 is consistent with
the theoretical one (Figure S9a,b) confirming the purity of
the bulk. The water content was established by thermo-
gravimetric analysis (TGA, Figure S10) and elemental
CHN analyses (Supporting Information). TGA of MOF 2
shows a fast mass loss from room temperature to ca. 150
°C. The estimated weight loss value is 32%, which corre-
sponds to the 72 crystallization water molecules hosted in
the pores. This abrupt loss in mass is followed by a sort of
XPS measurements of MOF 2 under an H atmosphere
2
within the XPS unit, at 100 ºC (Figure S8, right), show that
III
the original Fe signal remains unaltered, which supports
III
the stability of Fe in the MOF when dissociating H2.
Diffuse reflectance ultraviolet–visible (DR UV–vis, Figure
S14) measurements confirm the stability of the hexa–
III
aqueous Fe complex during the hydrogenation reac-
4
1
tion, and PXRD pattern after catalysis (Figure S9c)
showed that the material remains crystalline with no
evidence of nanoparticles (NPs) formation. All these re-
sults are in agreement and strongly support both the
“
plateau” until ca. 275 °C with a very smooth mass loss
which fits well with the loss of the water molecules coor-
dinated to iron(III) cations. After this “pseudo-plateau”,
decomposition starts.
III
protecting role of MOF’s channels and that the single Fe
site is responsible for the catalysis.
Prior to the gas–phase catalysis, the permanent porosity
O
O
O
O
M
O
O
M
O
of 2 was confirmed by means of the N and the CO ad-
O
O
Fe
2
2
M
M
O
O
O
O
Fe
O
O
O
Fe
O
O
O
Fe
O
O
O
M
O
Fe
O
O
O
M
O
O
Fe
O
Fe
OO
Fe
O
O
O
M
O
sorption isotherms at 77 and 273 K, respectively (Figures
Fe
M
O
O
O
A
O
O
B
O
C
O
O
M
O
O
M
M
Fe
S11 and S12). N isotherm shows an enhancement of the
O
2
3
1
accessible void space for 2 compared with the ancestor 1,
with a calculated Brunauer–Emmett–Teller (BET) surface
2
area of 1189 m /g with a calculated pore size of 1.38 nm.
III
This behavior, showing an increase of a 30% in the maxi-
Figure 3. Structures of a) ZrO doped with Fe atoms, b)
2
III
mum amount of N adsorbed compared to the isomor-
2
ZrO impregnated with Fe NPs, and c) TiO impregnated
2
2
3
1
III
phous compound 1, suggests an enhanced structural
stability after the PS cation metathesis to yield 2.
with planar Fe oxide NPs.
III
To study if single Fe sites intrinsically dissociate H2
without acetylene or ethylene participation, isotopic
H /D exchange experiments under a steady flow of Ar
2
2
were performed. The results (Figure S15) show the in-
creasing formation of H–D at expenses of H and D ,
2
2
when going from 25 to 125 °C, which strongly supports the
spontaneous dissociation of H over the catalytic hexa–
2
III
aqueous Fe site, under heating conditions. With this
data in hand, it seems reasonable that other related aqua–
III
, hydroxo– or oxo–Fe single sites, such as those in inor-
ganic oxides, may dissociate H and perform the hydro-
2
genation of 1% acetylene in ethylene streams under front–
end conditions. Despite MOF 2 is relatively cheap and
easy to prepare in large amounts, the study was extended
to even cheaper and more robust materials. Figure 3
Figure 2. Acetylene (blue squares) and ethane (red rhom-
buses) amounts in ppm during the continuous hydrogena-
tion of acetylene (1.2%) in an ethylene flow catalyzed by
MOF 2 at 150 °C.
III
shows the three different types of inorganic oxo–Fe
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structures prepared, characterized and tested in reaction
see SI, Figures S16–S23, for details).
ginal activity at 200 °C (Figure S26). These results illus-
trate the lack of catalytic activity for Fe O NPs, either
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(
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supported or not.
A new nFe –nZrO solid with smaller Fe oxide NPs
2
III
Structure A consists in isolated Fe atoms (10 wt%)
III
III
2
O
3
embedded into a nano–ZrO (≈25 nm) framework (Fe –
2
4
2
III
showed a significant better catalytic activity (Figure S27).
nZrO ), with a homogeneous distribution of Fe atoms
III
2
Indeed, Fe –nZrO doped with just 1 wt% Fe, thus having
2
along the oxide network, which lefts 0.5 wt% Fe loading
on surface, more or less comparable with MOF 2. Com-
plementary, structure B consists in a 1 wt% of Fe O clus-
in surface 0.05% Fe, works better and at lower tempera-
tures than the nanoparticulated Fe O (Figure S28), which
2
III
3
2
3
strongly supports that isolated Fe –O sites are catalytical-
ters (≈5 nm) supported on nanoZrO (nFe O –nZrO ), and
2
2
3
2
III
III
ly more active than extended Fe –O– Fe species. In
accordance with this, electronic paramagnetic resonance
(EPR) measurements (Figures S29) show that the signals
structure C consists in 0.5 wt% of planar Fe O NPs (≈1
2
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nm) supported on nanoTiO (≈25 nm), which maximizes
2
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the Fe –support oxide on surface and, thus, constitutes
an intermediate case between isolated oxo–Fe sites
III
III
corresponding to isolated Fe oxide sites (g=4.2, 9.0)
III
3
increase relatively to Fe oxide clusters (g=2.0) for 1 wt%
(
structure A) and 3D Fe O NPs (structure B). For the
2
3
45
Fe–nZrO2, and magnetic susceptibility (Figure S30) con-
sake of comparison, commercially–available, isolated
Fe O NPs were also tested in reaction. For all catalysts,
4
6
firms these results. Even though the presence of a small
3
4
III
0
II
percentage of higher nuclearity Fe oxide units cannot be
no Fe and only minor amounts of oxo–Fe were found,
together with the major oxo–Fe species (see SI).
III
completely discarded, spectroscopic measurements to-
gether with the synthesis procedure, which assures a
statistical distribution of Fe(III) in the ZrO2 structure,
strongly support that isolated Fe(III) oxide are the major
catalytic species. 0.5 wt% nFe O –nTiO , structure C in
2
3
2
H2
Figure 3, shows an intermediate hydrogenating activity
III
between isolated and nanoparticulated oxo–Fe sites
(
Figure S31), which is reasonable since the solids present
III
few layers of O–Fe sites in intimate contact with TiO2,
thus approaching isolated sites in structure A. An 8-hour
time experiment (Figure S32) shows that the catalyst is
quite robust, keeping a complete acetylene conversion
Ar
H-D
III
with levels of ethane <10%. Despite having more Fe on
D2
surface, the hydrogenation of acetylene does not proceed
III
2
5 ºC
125 ºC
15000
further than with MOF 2 or Fe –ZrO , which clearly re-
2
III
flects the importance of having isolated Fe –O sites for
5
000
10000
the industrial hydrogenation.
Time (s)
III
Figure 4. Isotopic H /D exchange over Fe –ZrO , with
2
2
2
temperature increasing from 25 to 125 ºC after 17500 s (5 h). A
constant Ar flow is used as a reference.
Figure 4 shows the isotopic H /D exchange experiment
2
2
III
for catalyst Fe –ZrO , and formation of H–D can be clear-
2
ly seen even at 25 °C, with a rapid increase up to 50 °C,
and then remaining steady up to 125 °C. Figure 5 shows
that, consistent with its lower temperature for H dissoci-
2
III
ation compared to MOF 2, Fe –ZrO catalyzes the hydro-
2
Figure 5. Acetylene and ethane amounts (in ppm) during the
genation of acetylene at just 100 °C and with similar levels
of efficiency (<10 ppm acetylene and ethane below 15%
during 3 h reaction time). The catalyst works up to 150 °C
continuous hydrogenation of acetylene (1.2%) in an ethylene
III
flow catalyzed by Fe –ZrO at 100 °C.
2
(
Figure S24) with a similar efficiency than at 100 °C, thus
Figure 6A shows the result for the hydrogenation in
2
47
providing a reasonable operational window (OW) of tem-
perature to control reaction runaways in industrial condi-
tions. DR UV–vis measurements (Figure S25) confirm the
batch of d –acetylene, with a rapid exchange of D by H
atoms, up to 43%, while, in contrast, Figure 6B shows that
acetylene barely exchanges its protons with D2 under
similar hydrogenation conditions (<1%). These results
indicate that the hydroxyl groups, and perhaps also water
present on the solid oxide, interact with the alkyne. The
kinetic isotopic effect (KIE) calculated for the hydrogena-
tion in batch with H and D is 3.2, in line with previous
stability of the material at high temperatures. Notice that
III
the operability conditions for Fe –ZrO are reasonable
2
similar to current Pd–Al O industrial catalysts (70–140
2
3
3
8,43,44
III
°
C, ca. 70 °C OW).
In contrast to Fe –ZrO , isolated Fe O NPs do not
2
2
2
3
4
3
results with other alkynes. This result confirms that H
show any catalytic activity for the hydrogenation of acety-
lene, and nFe O –nZrO (structure b) only showed a mar-
2
dissociation intervenes in the rate-determining step of the
reaction. Figure 6C shows a proposed mechanism for the
2
3
2
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III
reaction, where H dissociates on the isolated Fe –O site
5.67; N, 4.26%. Found: C, 23.61; H, 5.61; N, 4.29%. IR
(KBr): ν = 1608 cm (C=O).
2
–1
1
2
3
4
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7
8
9
with the assistance of a hydroxyl group and, then, trans-
ferred to acetylene, which coordinates and exchanges H
atoms with neighboring hydroxyl groups. The adsorption
of acetylene (pKa ≈29) on the active sites of the solid
through acid–base interactions may explain its higher
reactivity respect to ethylene ((pKa ≈50).
Aiming at exploring possible industrial applications, a
multigram-scale procedure was also carried out. So, a
much higher amount of a polycrystalline sample of 1 (4.14
g, 1.2 mmol), was suspended in a H O/CH OH (1:1) solu-
2
3
II
tion of (NH ) Fe (SO ) ·6H O (0.46 mg, 1.2 mmol) for 12
4
2
4
2
2
hours under a mild stirring. The process was repeated 5
times. Finally, the product was collected by filtration,
washed with a H O/CH OH (1:1) solution and air-dried.
2
3
1
1
1
1
1
1
1
1
1
1
2
2
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Anal.: calcd. for Cu Ni Fe C H N O (3944.4): C, 23.75;
6 4 2 78 222 12 118
H, 5.67; N, 4.26%. Found: C, 23.51; H, 5.65; N, 4.31%. IR
–1
(KBr): ν = 1603 cm (C=O).
III
Preparation of Fe -nZrO : The proper amount of
2
ZrOCl ·8H O and FeCl ·6H O precursors (23.5 mmoles in
2
2
3
2
total) were dissolved in 35 mL of milliQ water, then 27
mmoles of urea were added to the solution. The solution
was transferred into one Teflon cup of 100 mL and intro-
duced in a microwave oven. The temperature was in-
Figure 6. A, B) Isotopic experiments. C) Proposed mecha-
III
nism for acetylene hydrogenation on isolated Fe –O catalyt-
o
o
ic sites.
creased at 20 C/min until 220 C, with a dwell time of 10
minutes. Then, the vials were allowed to cool to room
temperature and the precipitates were washed and centri-
fuged several times. The material was dispersed in water
and dialyzed until no chloride ions were detected. Finally,
water was removed by rotatory evaporation. Following
CONCLUSIONS
III
In summary, isolated Fe –O sites on solids catalyze
chemoselectively the hydrogenation of acetylene in eth-
ylene streams under simulating front–end industrial con-
ditions. The straightforward preparation of a MOF em-
this method, the material obtained is ZrO with the te-
2
III
bedding accessible Fe sites within its pores, by means of
tragonal structure as the main crystallographic phase with
iron introduced in the zirconia structure.
a SC to SC PS cation metathesis, allowed to resolve the
structure by single crystal X–ray diffraction, confirming
Preparation of nano-ZrO2: 23.5 mmoles of
III
the nature of the Fe active site. Translation of this Fe
ZrOCl ·8H O were dissolved in 35 mL of milliQ water.
2
2
active site to more robust and simple metal oxides pro-
duced new and cheap, readily available solid catalysts for
the industrial reaction, showcasing the cross fertilization
between atomically–precise crystalline MOF structures
and well–defined supported isolated metal atoms. Beyond
mechanistic considerations, the catalysts here presented
are just made of relatively non–toxic and inexpensive
metals such as Fe, Ti, Cu or Zr, in contrast to the com-
mercial catalysts, which are based on Pd with Ag or Pb
The solution was transferred into one Teflon cup of 100
mL and introduced in a microwave oven. The tempera-
o
o
ture was increased at 20 C/min until 220 C, with a dwell
time of 10 minutes. Then, the vials were allowed to cool to
room temperature and the precipitates were washed and
centrifuged several times. The material was dispersed in
water and dialyzed until no chloride ions were detected.
Finally, water was removed by rotatory evaporation. Fol-
lowing this method, the material obtained is ZrO with
2
48–50
additives.
monoclinic structure.
Preparation of nFe O -nZrO : The metal oxide was
2
o
3
2
EXPERIMENTAL SECTION
wet impregnated at 45 C with a solution that contained
III
III
2
Preparation
of
[Fe (H O) ][Fe (µ–
2
6
the proper amount of Fe(acac) dissolved in 5 mL of ace-
II
II
3
O) (H O) ]1/2{Ni 4[Cu 2(Me mpba) ] } · 72H O (2): Well-
2
2
6
3
2
3
2
tone. After the impregnation, the materials were dried
formed hexagonal green prisms of 2, suitable for X-ray
diffraction, were obtained by soaking crystals of 1 (ca. 51.8
o
overnight at 110 C and calcined with a heating rate of 5
o
o
C/min at 500 C during 2 hours.
mg, 0.015 mmol) in an aqueous solution of
II
Preparation of nFe O -nTiO : 1 g of TiO support was
2
3
2
2
(
NH ) Fe (SO ) ·6H O (5.8 mg, 0.015 mmol) for 24 hours
4
2
4
2
2
weighed and a solution with the corresponding amount of
under aerobic conditions. The process was repeated five
more times to ensure the total replacement of nickel at-
oms hosted in the pores by iron ones. The cation-
exchanged crystals (2) have the same size and shape as
those of the ancestor material (1), ruling out a possible
dissolution-recrystallization mechanism for this system
FeCl in 15 ml distilled water was added. The mixture was
2
magnetically stirred at 250 rpm for a few minutes. 50 mg
of citric acid was added and the mixture was left to stir for
further two minutes. 120 mg of the reducing agent, sodi-
um borohydride (NaBH ), were added under continuous
4
5
1
stirring, and the mixture was capped with a rubber sep-
tum having a needle piercing, and stirred for 16 h at 250
rpm. After this time, the solid was filtered with a Büch-
ner-Kitasato flask under vacuum. The solution was dou-
ble-filtered to catch smaller particles, and a dropper was
and strongly suggesting a solid-state process. The crys-
tals were washed with a H O/CH OH (1:1) solution several
2
3
times, isolated by filtration on paper and air-dried. Anal.:
calcd. for Cu Ni Fe C H N O (3944.4): C, 23.75; H,
6
4
2
78 222 12 118
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used to load small quantities of the catalyst solution on to
(7)
Albani, D.; Capdevila-Cortada, M.; Vilé, G.; Mitchell, S.;
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Martin, O.; López, N.; Pérez-Ramírez, J. Angew. Chemie Int. Ed.
the filter paper. The remaining solid on the filter paper
was rinsed with distilled water followed by acetone. The
filter paper containing the solid catalyst was carefully
transferred into a glass vial and dried for 24 h under vac-
uum.
2017, 56 (36), 10755.
(
(
8)
9)
Liu, L.; Concepción, P.; Corma, A. J. Catal. 2016, 340, 1.
Sorribes, I.; Liu, L.; Corma, A. ACS Catal. 2017, 7 (4),
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(10)
Furukawa, H.; Cordova, K. E.; O’Keeffe, M.; Yaghi, O.
Hydrogenations in flow. Typically, 25 mg of solid cat-
M. Science 2013, 341, 974.
3
(11)
Li, J.-R.; Kuppler, R. J.; Zhou, H.-C. Chem. Soc. Rev.
alyst (ca. 0.14 cm ) were placed in a fixed bed tubular
2009, 38 (5), 1477.
reactor, conditioned before each experiment with N gas
2
(
12)
X. ACS Catal. 2014, 4 (2), 361.
13) Valvekens, P.; Vermoortele, F.; De Vos, D. Catal. Sci.
Technol. 2013, 3 (6), 1435.
14) Mon, M.; Lloret, F.; Ferrando-Soria, J.; Martí-Gastaldo,
Gascon, J.; Corma, A.; Kapteijn, F.; Llabrés i Xamena, F.
(
see SI for details) and connected to a GC instrument, and
0
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ethylene/acetylene (1 %) and H were passed at flowrates
2
(
and pressures of 2 and 4 ml/min, and 1 and 2 bars, respec-
tively, at temperatures between 70 and 200 °C.
(
C.; Armentano, D.; Pardo, E. Angew. Chemie Int. Ed. 2016, 55
(37), 11167.
Hydrogenations in batch. Acetylene (1 bar) and H (3
2
bars) were charged in a pressure resistant reactor with 10
mg of the desired catalyst, and the mixture placed in a
pre-heated oil bath at 150 °C. Gas aliquots were periodi-
cally taken and analyzed by GC-MS.
(15)
Mon, M.; Ferrando-Soria, J.; Grancha, T.; Fortea-Pérez,
F. R.; Gascon, J.; Leyva-Pérez, A.; Armentano, D.; Pardo, E. J. Am.
Chem. Soc. 2016, 138 (25), 7864.
(
16)
80.
17)
(21–24), 2490.
18) Li, P.; Modica, J. A.; Howarth, A. J.; Vargas L., E.;
Inokuma, Y.; Arai, T.; Fujita, M. Nat. Chem. 2010, 2 (9),
7
ASSOCIATED CONTENT
(
Kitagawa, S.; Matsuda, R. Coord. Chem. Rev. 2007, 251
Supporting Information Available. Physical techniques.
Crystallographic and catalytic details. Figures S1–S32. Tables
S1–S2. CCDC reference number: CCDC–1835021. This material
is available free of charge via the Internet at
http://pubs.acs.org.
(
Moghadam, P. Z.; Snurr, R. Q.; Mrksich, M.; Hupp, J. T.; Farha,
O. K. Chem 2016, 1 (1), 154.
(19)
Fortea-Pérez, F. R.; Mon, M.; Ferrando-Soria, J.; Boro-
nat, M.; Leyva-Pérez, A.; Corma, A.; Herrera, J. M.; Osadchii, D.;
Gascon, J.; Armentano, D.; Pardo, E. Nat. Mater. 2017, 16 (7), 760.
(20) Ji, S.; Chen, Y.; Fu, Q.; Chen, Y.; Dong, J.; Chen, W.; Li,
Z.; Wang, Y.; Gu, L.; He, W.; Chen, C.; Peng, Q.; Huang, Y.;
Duan, X.; Wang, D.; Draxl, C.; Li, Y. J. Am. Chem. Soc. 2017, 139
AUTHOR INFORMATION
Corresponding Author
*
To whom correspondence should be addressed. E–mail:
(
29), 9795.
21) Liu, H.; Chang, L.; Bai, C.; Chen, L.; Luque, R.; Li, Y.
Angew. Chemie Int. Ed. 2016, 55 (16), 5019.
22) Li, B.; Leng, K.; Zhang, Y.; Dynes, J. J.; Wang, J.; Hu, Y.;
emilio.pardo@uv.es; donatella.armentano@unical.it; anley-
va@upv.itq.es; acorma@upv.itq.es.
(
Notes
(
The authors declare no competing financial interests.
Ma, D.; Shi, Z.; Zhu, L.; Zhang, D.; Sun, Y.; Chrzanowski, M.; Ma,
S. J. Am. Chem. Soc. 2015, 137 (12), 4243.
(23) Genna, D. T.; Wong-Foy, A. G.; Matzger, A. J.; Sanford,
M. S. J. Am. Chem. Soc. 2013, 135 (29), 10586.
ACKNOWLEDGMENT
This work was supported by the MINECO (Spain) (Projects
CTQ2016–75671–P, CTQ2014–56312–P, CTQ2014–55178–R and
Excellence Units “Severo Ochoa” and “Maria de Maeztu”
SEV–2016–0683 and MDM–2015–0538) and the Ministero
dell’Istruzione, dell’Università e della Ricerca (Italy) (FFABR
(24) Abhervé, A.; Grancha, T.; Ferrando-Soria, J.; Clemente-
León, M.; Coronado, E.; Waerenborgh, J. C.; Lloret, F.; Pardo, E.
Chem. Commun. 2016, 52 (46), 7360.
(25) Mon, M.; Rivero-Crespo, M. A.; Ferrando-Soria, J.;
Vidal-Moya, A.; Boronat, M.; Leyva-Pérez, A.; Corma, A.; Her-
nández-Garrido, J. C.; López-Haro, M.; Calvino, J. J.; Ragazzon,
G.; Credi, A.; Armentano, D.; Pardo, E. Angew. Chemie Int. Ed.
2017). M. M. thanks the mineco for a predoctoral contract.
Thanks are also extended to the Ramón y Cajal Program (E.
P.) and the “Suprograma atracció de talent-contractes post-
doctorals de la Universitat de Valencia” (J. F.-S.). A. L.-P. also
thanks to fBBVA for the concession of a young investigator
grant.
2018, 57 (21), 6186.
(26) Mon, M.; Bruno, R.; Ferrando-Soria, J.; Bartella, L.; Di
Donna, L.; Talia, M.; Lappano, R.; Maggiolini, M.; Armentano,
D.; Pardo, E. Mater. Horizons 2018, doi: 10.1039/C8MH00302E.
(27) Bloch, W. M.; Champness, N. R.; Doonan, C. J. Angew.
Chemie Int. Ed. 2015, 54 (44), 12860.
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