Synthesis of Densely Packaged, Ultrasmall Pt02 Clusters within a Thioether-Functionalized MOF: Catalytic Activity in Industrial Reactions at Low Temperature

Article abstract of DOI:10.1002/anie.201801957

The gram-scale synthesis, stabilization, and characterization of well-defined ultrasmall subnanometric catalytic clusters on solids is a challenge. The chemical synthesis and X-ray snapshots of Pt⁰₂ clusters, homogenously distributed and densely packaged within the channels of a metal–organic framework, is presented. This hybrid material catalyzes efficiently, and even more importantly from an economic and environmental viewpoint, at low temperature (25 to 140 °C), energetically costly industrial reactions in the gas phase such as HCN production, CO₂ methanation, and alkene hydrogenations. These results open the way for the design of precisely defined catalytically active ultrasmall metal clusters in solids for technically easier, cheaper, and dramatically less-dangerous industrial reactions.

Full text of DOI:10.1002/anie.201801957

A Journal of the Gesellschaft Deutscher Chemiker
Angewandte
International Edition Chemie
www.angewandte.org
Accepted Article
Title: Synthesis of densely-packaged, ultrasmall Pt02 clusters within
a thioether functionalised MOF and their catalytic activity in
industrial reactions at low-temperature
Authors: Marta Mon, Miguel A. Rivero–Crespo, Jesús Ferrando-Soria,
Alejandro Vidal–Moya, Mercedes Boronat, Antonio Leyva-
Pérez, Avelino Corma, Juan C. Hernandez-Garrido, Miguel
López–Haro, José J. Calvino, Giulio Ragazzon, Alberto Credi,
Donatella Armentano, and Emilio Pardo
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To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.201801957
Angew. Chem. 10.1002/ange.201801957
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Synthesis of densely-packaged, ultrasmall Pt0
clusters within a
2
thioether functionalised MOF and their catalytic activity in
industrial reactions at low–temperature
[
a]
[b]
[a]
[b]
Marta Mon, Miguel A. Rivero–Crespo, Jesús Ferrando–Soria, Alejandro Vidal–Moya, Mercedes
[
b]
[b]
[b]
[c,d]
Boronat, Antonio Leyva–Pérez,* Avelino Corma,* Juan C. Hernández–Garrido, Miguel López–
Haro,[c,d] José J. Calvino,[c,d] Giulio Ragazzon [e] Alberto Credi,[e,f] Donatella Armentano* and Emilio
[g]
,
Pardo*[a]
Abstract:
The
gram-scale
synthesis,
stabilization
and
strategy to overcome the mentioned problems. Nevertheless,
much efforts are still needed to exactly control atomicity,
electronics, structure and metal loading of the sMCs.
characterization of well-defined ultrasmall subnanometric catalytic
clusters on solids represent a challenge. Here, we report the
0
Metal–Organic Frameworks (MOFs),[9–11]
chemical synthesis and X-ray snapshots of Pt
2
clusters,
a
type of
homogenously distributed and densely-packaged within the
channels of a metal-organic framework. This novel hybrid material
catalyzes efficiently, and even most important from an economic and
environmental viewpoint, at low temperature (25 to 140 ºC),
energetically–costly industrial reactions in the gas phase such as
crystalline porous materials, are, potentially, good platforms to
synthesize sMCs in a controlled manner. In this context,
information about their nature might be gained by single crystal
X–ray crystallography (SC–XRC),[12,13] in combination with more
common characterization techniques for solid supported metals
such as X–ray photoelectron spectroscopy (XPS), Fourier
transform infrared spectroscopy under CO (FTIR–CO) or
aberration–corrected scanning transmission electron microscopy
2
hydrogen cyanide (HCN) production, carbon dioxide (CO )
methanation and alkene hydrogenations. These results open the
way for the design of precisely–defined catalytically active ultrasmall
metal clusters in solids for technically easier, cheaper and
dramatically–less dangerous industrial reactions.
(AC–STEM).[12,14] Despite some examples of MOFs hosting
small metal nanoclusters of 1–3 nm,[
15–19]
it is difficult to find
MOFs with metal species below the nanometer.[ A successful
development of this type of materials, also considering the well–
known ability of MOFs to adsorb gas molecules,[11] could lead to
12]
Sub–nanometer metal clusters (sMCs),[1–5] consisting of small
aggregations of atoms exposed to the external environment,
have emerged as excellent catalysts for organic reactions of
industrial interest.[6,7] Unfortunately, their synthesis and
a more efficient, economic and safe way to carry out a variety of
[20]
reactions of technological interest
gases.
requiring the activation of
[
8]
stabilization is still a challenge. Supporting sMCs on the
appropriate porous matrix[5] has been proven as an efficient
Herein, we report the chemical synthesis, and structural
and electronic well–defined characterization, of Pt0
clusters
2
within the functional channels of a MOF, decorated with
thioether recognition sites, intrinsically devoted for this purpose.
This new synthetic route to sMCs represent a step-forward
[
[
a]
b]
M. Mon, Dr. J. Ferrando-Soria, Dr. E. Pardo
Instituto de Ciencia Molecular (ICMOL). Universitat de València
Paterna 46980, València (Spain)
E-mail: emilio.pardo@uv.es
M. A. Rivero–Crespo, A. Vidal–Moya, Dr. M. Boronat, Dr. A. Leyva–
Pérez, Prof. Dr. A. Corma
Instituto de Tecnología Química (UPV–CSIC). Universidad
Politècnica de Valencia–Consejo Superior de Investigaciones
Científicas. Avda. de los Naranjos s/n, 46022 Valencia, Spain
E-mail: anleyva@itq.upv.es, acorma@itq.upv.es
Dr. J. C. Hernández–Garrido, Dr. M. López–Haro, Prof. J. J. Calvino
Departamento de Ciencia de los Materiales e Ingeniería Metalúrgica
y Química Inorgánica. Facultad de Ciencias. Universidad de Cádiz,
Campus Río San Pedro, 11510 Puerto Real, Cádiz, Spain
Dr. J. C. Hernández–Garrido, Dr. M. López–Haro, Prof. J. J. Calvino
Instituto Universitario de Investigación en Microscopía Electrónica y
Materiales (IMEYMAT). Facultad de Ciencias. Universidad de
Cádiz, Campus Río San Pedro, 11510 Puerto Real, Cádiz, Spain
[12]
respect a previously described method, whose applicability is
limited to anionic MOFs. The obtained Pt0
–MOF material
catalyzes reactions, very important from an industrial point of
view, such as the room temperature NH
CN production[21], after
concomitant activation of CO and NH
2
4
3
, the methanation of
[
22–24]
CO
<
2
and the hydrogenation of ethylene and ≤C6 olefins at
140 ºC, showing the high intrinsic catalytic activity of the Pt0
2
sMCs for a variety of industrial reactions in the gas phase[
25]
[
c]
d]
Figure 1 shows the synthesis of the Pt0
2
–MOF material in 3
steps. First, a robust and water–stable 3D MOF, prepared with a
ligand derived from the amino acid L-methionine, of formula
[
II
II
6 3 2 2 2
{Ca Cu [(S,S)–methox] (OH) (H O)} 16H
O (1)[26,27] (Figure 1a),
.
featuring pores decorated with thio–alkyl chains, was prepared
as the starting material. Then, Pt2 cations were incorporated by
+
[
[
[
e]
,
G. Ragazzon Prof. Dr. Alberto Credi
Dipartimento di Chimica “G. Ciamician”, University of Bologna.
Via Selmi 2, 40126 Bologna, Italy
anchoring the metal salt K
the coordination network, yielding (Pt Cl
O)} . 13H
methox] (OH) (H O (2) (Figure 1b). Finally, the Pt
units were obtained by reduction of 2 with NaBH , to give
2 4
[PtCl ] to 1 through the S atoms of
II
II
II
2 2 6
) @{Ca Cu [(S,S)–
f]
Prof. Dr. Alberto Credi
3
2
2
2
2
Dipartimento di Scienze e Tecnologie Agro–alimentari, University of
Bologna, Viale Fanin 50, 40127 Bologna, Italy
Dr. D. Armentano
4
Pt0
0.5(Pt Cl
II
)@{Ca Cu
II
II
[(S,S)–methox]
(OH)
(H
2
O)}
.
(
2
)
2
6
3
2
2
15H O
g]
Dipartimento di Chimica e Tecnologie Chimiche
Università della Calabria. 87030, Rende, Cosenza, Italy
E-mail: donatella.armentano@unical.it
(3) (Figure 1c). Interestingly, 2 and 3 show a high loading of
platinum atoms (ca. 17 wt% for both 2 and 3), 50% of which are
0
clusters in 3. The nature of the Pt0
Pt
2
2
units in 3 was
Supporting information for this article is given via a link at the end of
the document.
established by combining SC–XRC using synchrotron radiation
Figures 1 and S1–S8) and AC–STEM (Figures 2 and S9–S14),
(
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which allowed unprecedented snapshots of such tiny clusters at
the atomic level. Inductively coupled plasm–mass spectrometry
Information, Figures S15, S16 top and Table S1), in combination
with XPS, FTIR–CO spectroscopy (Figures S17 and S18) and
DFT calculations (Figure S19), were also used to establish the
structure and oxidation state of Pt.
(
ICP–MS), elemental analysis, powder X–ray diffraction (PXRD)
and thermo–gravimetric (TGA) analyses (see Supporting
Figure 1. Crystal structures of the MOFs 1 (a) 2 (b) and 3 (c). d, determined by single-crystal X-ray diffraction. Perspective views, in detail, of a channel of 3 in
the ab (left) and bc (right) planes. Copper and calcium atoms from the network are represented by cyan and blue polyhedra, respectively, whereas organic ligands
are depicted as grey sticks. Yellow and purple spheres represent S and Pt atoms, respectively. Dashed lines represent the Pt···S interactions. e. Fragment of a
channel of 3 emphasizing the interactions with the network. Pt–S and Pt…O interactions are represented by yellow and blue dashed lines, respectively.
The crystal structures of 2 and 3 are isomorphous and
crystallize in the chiral P6 space group, like the ancestor 1,
with a Pt–Pt distance of 2.49(6) Å are unambiguously observed
(Figures 1b,c and S1b–S5). As far as we know, no reports on
3
exhibiting a common chiral honeycomb–like 3D calcium(II)–
copper(II) framework. These uni–nodal six–connected acs
crystallographically precise Pt0
2
dimers appeared so far, the only
0
0
experimental data recording on Pt –Pt distance in sMCs
indicates a value of 2.65 Å, extrapolated from X–ray absorption
9
. 6
networks (point symbol 4 6 ) feature hexagonal channels,
where the highly flexible thioalkyl chains (Figures S1–S5 and
video S1), remain confined and adopt conformations depending
on the nature of guests, Pt2+ in 2 (Figures 1a, S1 and S3) or both
fine structure spectrum (EXAFS).[5] Pt0
dimers weakly interact
2
also with oxamate moieties with Pt···O distances of 2.79(1) and
2.80(1) Å (Figures 1d–e; see also Supporting Information
Figures S4 and S5). Periodic DFT calculations support the
crystallographic characterization of 3, with optimized distances
Pt2+ and Pt0
values of the Pt –S bond distances [2.46(5) and 2.34(3) Å (2)
NCs in 3 (Figures 1b, 1c, S2, S4 and S5). The
2
2
+
0
0
0
2+
(
Figure S1a) and 2.25(3)-2.41(3) Å (3), Figure S2b] are similar to
Pt –Pt = 2.43 Å, Pt –S = 2.18 Å, Pt –S = 2.32 – 2.34 Å and
[
28,29]
2+
typical values reported in the literature.
the Pt –S distance is 2.30(4) Å (3) (Figure S1b). Each Pt ion is,
On the other hand,
Pt –Cl = 2.26 Å, and the proposed electronic distribution, with
0
2+
0
calculated atomic charges of -0.10 and -0.03 for Pt and 0.46 –
0.49 e for Pt (Figure S19).
-
2+
as expected, further surrounded by chloride atoms [Pt-Cl =
2
.52(4) Å in 2 and 2.42(4)/2.48(4) Å in 3] (see crystallographic
Figure S6 shows a plausible mechanism for the formation
section in SI). The conformation of the MOF’s thioalkyl arms
evidences chain intrinsic flexibility, with one of the two
asymmetric moieties exhibiting a distended conformation inward
the pores, grasping a fraction of guest molecules, and forcing
the other one in an extremely bent conformation of the methyl
groups to pinpoint a 50% of total Pt2+ ions in poorly accessible
interstitial sites, pointing along c axis (Figures S1a, S3–S5). The
conformation observed in 2 (Figures S1a and S3) is also
of the Pt0
2
dimers in 3, driven by the flexibility of the thio–ether
2
+
groups anchoring Pt metals in 2, which most–likely approach
2
+
two neighboring Pt –S units located inside the pores, to build
the Pt0
units after the reduction process. Meanwhile, the
2
mononuclear Pt2 complexes residing in hindered interstitial
voids are not reduced (Figure S2). Interestingly, the virtual
diameter of the channels increases from ca. 0.3 nm in the
precursor material 1 to ca. 0.8 nm in 2 and 3 (Figures S7 and
+
adopted in 3 (Figures S2b, S4–S5a) where, in turn, Pt0
dimers
2
2
S8), and N adsorption isotherms at 77 K (Figure S16 bottom)
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confirm the increased permanent porosity of both 2 and 3
compared to the starting material 1.[27] The Brunauer-Emmett-
Teller (BET) surface areas calculated for 1, 2 and 3 are 153, 487
stabilization transform, wavelet–based filtering and background
subtraction (Figures S13a–c), followed by template matching
and pair correlation analysis tandem (Fig S13d–f), allowed
detecting neighbors and next–nearest neighbors of each
isolated atom on the Z–contrast images. This gives a pair
correlation function g(r) (see Figures 2b–d, S13 and S14), which
informs about the probability of finding the center of an atom at a
given distance from the center of another atom (further details
can be found in the Supporting Information). Applying this
analysis to a large set of experimental images (two of them are
shown in Figure S14), provided an average Pt–Pt distance of
2
and 453 m /g, respectively, with pore sizes of 0.22, 0.61 and
0.57 nm, following a similar trend to that observed in the crystal
structures (see Supporting Information for details).
0.262 nm. Indeed, this value is in very good agreement with
single–crystal X–ray diffraction measurements.
Deconvoluted XPS of compound 2 (Figure S17a) shows a
typical Pt4f7/2 doublet for Pt2+ at 73.8 and 77.2 eV, while 3
(
Figures S17b–c) shows two additional peaks at 72.1 and 75.6
0
eV, which correspond to Pt . The progressive increase of the
latter at expenses of the former when using increasing amounts
of reducing agent, up to 50%, is in good agreement to the
expected reduction of the Pt2 accessible atoms when treated
with solvated BH -
spectroscopy of 2 (Figure S18a) shows three signals at 2154,
+
4
in solution. Low–temperature FTIR–CO
-1
2
136 and 2104 cm , which can be assigned to free CO, CO
2
+
coordinated to Pt atoms in the pores, and CO coordinated to
the Pt2+ atoms in interstitial positions, respectively[30]. In contrast,
3
(Figure S18b) shows a dramatic decrease of the signal at
-1
2136 cm at expenses of the appearance of a new band at 1870
-1
0
cm , which can be assigned to CO coordinating two Pt
atoms.[ These results strongly support that only one fraction of
31]
the Pt2+ atoms in 2, probably the most accessible ones, is
Figure 2. AC–HAADF–STEM analysis of 3. The porous crystalline structure of
the MOF is observed in (a). After denoising AC–HAADF–STEM image, the
spatial distribution of the ultrasmall Pt clusters is clearly observed (b).
Visualization is further improved after background subtraction and color
displayed; inset in (b) corresponds to the dash–squared area. Lower inset in
reduced with BH
4
–, while the inaccessible, interstitial Pt2+ atoms
are unaltered during the process (see Figure S6).
UV–visible absorption spectra obtained from diffuse
reflectance measurements (Figure S20) reveals that compound
(
b) illustrates an intensity profile on the Pt dimer marked in the upper inset.
Overlay of the denoised AC–HAADF–STEM image and the x–y coordinates
green dots) obtained after template matching is shown in (c). The pair
3
exhibits a significantly higher absorbance between 300 and
0
[32,33]
(
400 nm, which supports the presence of the Pt dimers,
correlation function from the processed image is plotted in (d). A zoom of the
small Pt–Pt distance range is shown as inset. The asterisk marks the position
of the highest probability Pt–Pt distance at 0.283 nm.
together with the d–d transitions between 600 and 900 nm
corresponding to Cu ions. PXRD patterns of 2 and 3 (Figure
S15) confirm the pureness of the bulk samples (being
isostructural to those crystals selected for SC–XRC), and that
the open–framework structures remain unchanged after the
insertion of the Pt salt in 2 (Figure S15a) and the reduction
process to yield 3 (Figure S15b). No peaks of Pt NPs or oxide
crystal structures in the PXRD pattern of 3 (Figure S15b) were
found, which is consistent with the characterization results
Figures 2, S9 and S10 show AC–STEM images of 3 with
high–angle annular dark field (HAADF) or Z–contrast imaging,
coupled with chemical elemental maps by X–EDS in Figure S10.
They allow a direct visualization of homogeneously distributed
single Pt atoms (Pt2+ cations located in interstitial sites) and Pt
dimers (inset of Figure 2b and Figure S9) on the preserved
crystalline framework, in accordance with SC–XRC
measurements. The same Pt dimers can be also inferred by
2
presented above, indicating that only Pt0
sMCs are formed after
2
the reduction process to yield 3. Finally, PXRD patterns after the
hydrogenation of ethylene in flow for 4 hours on stream up to 60
ºC (3’ exp in Figure S15b), also showed no peaks indicative of
agglomeration.
Figure 3a shows the results for the Pt–catalyzed reaction
3
of NH with CO at room temperature. Only 2 and 3 showed
2
HAADF-STEM images (Figure S11) of 3 after the hydrogenation
of ethylene in flow for 4 hours on stream up to 60 ºC (Figure
S11). The corresponding XEDS elemental mapping also shows
a very homogenous distribution of Pt atoms after catalysis
catalytic activity among 20 different Pt catalysts, including Pt
salts, complexes and supported nanoparticles, with an initial
(
(
Figure S12). Analysis of aberration corrected HR–TEM images
Figure S10a) allows to visualize the lattice fringes of the net,
-1
turnover frequency (TOF
(
(
0
) = 1260 h . The total turnover number
TON) for 3 was 56, double than for 2. Kinetic experiments
Figure S21) show that the 3–catalyzed reaction starts fast,
with interplanar spacing of 1.52 nm, which corresponds to (100)
planes of the MOF and 0.30 nm (500) thus confirming that 3
retains crystallinity (Figure S10a). The combination of advanced
image processing, based on combined Anscomb variance
without any induction period, and the reaction rate rapidly
decreases. In contrast, 2 presents a reaction induction period. If
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Angewandte Chemie International Edition
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one supposes that Pt 0
are the catalytically active species, as
wt%).[36] Temperature-programmed desorption of NH
coupled to mass spectrometry (TPD-MS), shows that NH
2
3
in 1 and 3,
indicated by the experiments with catalyst 3, the induction period
observed with catalyst 2 would be due to the time required to
3
desorbs unaltered at <120 ºC, together with some water, after
saturation of the samples at atmospheric pressure (Figure S25).
2
+
0
2
reduce Pt into Pt . For studying how the reaction occurs on
the catalyst, in–situ 13C and 15N cross–polarization magic angle
spinning nuclear magnetic resonance (CP/MAS–NMR)
experiments with 0.5 and 1 ML of isotopically labelled 13CO and
The N CP/MAS–NMR of 3 after adsorbing isotopically labelled
15
15NH
(0.2 mmol x g , 0.25 equivalents with respect to Pt) at low
-1
3
pressure and -196 ºC, further confirms the easy incorporation of
1
5
[37]
3
NH , respectively, were adsorbed in 3 at room temperature
3
NH to the MOF structure (Figure S26). Kinetic experiments at
and pressure. The results (Figure S22) show the progressive
different partial pressures of CO (PCO) and NH
maintaining a total pressure of 6 bars with N , show that the
initial reaction rate only depends on PNH3 and not on PCO, which
supports that the Pt sites are saturated with CO molecules and
that the coupling with NH catalytic sites, to form the
on the Pt0
amide intermediate, is the rate–determining step of the reaction.
Analysis of the post–mortem solid catalyst (Figure S27) clearly
shows the presence of two different cyanide species on the
3
(PNH3), while
disappearance of 13CO and 15NH
,
1
and the progressive
3
2
3
15
appearance of two new peaks at 165 ( C) and -255 ( N) ppm,
which can be assigned to adsorbed amide and oxime–type
species.[34] These results agree well with the formation of an
intermediate Pt amide species, which dehydrates directly to
2
3
2
NH
formation, as depicted in Figure 3a. Thus, it can be said that 3
has an extraordinary intrinsic catalytic activity for NH CN
formation, which energetically by–passes (H298= -20 kcal mol )
4 3
CN under the excess of NH and circumvents HCN
4
4 2
surface of 3, which can be assigned to NH CN and Pt –CN
-1
species, respectively, which explain the decrease of activity of
the catalyst during reaction. However, the results here open the
-1 [35]
the HCN formation (H298= +12 kcal mol )
NH adsorption isotherm (Figure S24) shows that the MOFs 1
and 3 incorporate ca. 25 wt% of NH , which approaches the
highest absorptivity values found in the literature for MOFs (20
(Figure S23). A
way for the design of Pt0
catalytic sites on more robust solids,
3
2
3
which will result in intrinsically very active and long stable
catalyst for HCN formation.
Figure 3. (a) Pt–catalysed synthesis of HCN at room temperature: Equation shows the reaction conditions: CO (4 bar, 1.5 mmol), NH
.0075 mmol Pt, and a plausible reaction mechanism. Table includes the set of Pt catalysts tested under these reaction conditions. (b) Pt–catalysed methanation
of CO : Equation shows the reaction conditions: 7 ml CO (1 atm, 0.28 mmol), 7 ml N (internal standard, 1 atm, 0.28 mmol), 7 ml H (4 atm, 1.12 mmol), MOF
catalyst 2 and 3 (8 wt%, 20 mg, 0.008 mmol metal) or M/Al (5 wt%, 32 mg, 0.008 mmol metal), 100–140 ºC, 6 hours. Table includes reaction values for
3
(2 bar, 0.75 mmol) and
0
2
2
2
2
2 3
O
reference literature catalysts and catalyst 3. (c) Pt–catalysed hydrogenation of ethylene: Equation shows the reaction conditions: 2 ml/min C
atmospheric pressure, 60 ºC, 50 mg 3 (0.010 mmol Pt). Table includes reaction values for reference literature catalysts and catalyst 3.
2 4 2
H , 6 ml/min H ,
Figure 3b presents the hydrogenation of CO
Sabatier reaction) at low temperature (<150 ºC) catalyzed by
the 2 and 3 and also by reference catalysts (further details
including TOFs can be found in Table S3).[23] As it can be seen,
catalyst 3 outperforms the rest of materials tested under the
2
to methane
low–temperature conditions, including the industrial catalyst Ru–
2
+
(
Al
2
O
3
. The lack of activity of 2 discards Pt sites as catalytic
0
active species, and indicates that Pt
hydrogenation of CO
reduced to Pt 0
, in contrast to the cyanide reaction. It can be
2
is the catalytic sites for the
and that the Pt2+ sites are not in–situ
2
2
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speculated that Pt2+ reduction occurs with CO, which is certainly
SEV–2012–0267 and MDM–2015–0538) and the Ministero
dell’Istruzione, dell’Università e della Ricerca (Italy) and the
Junta de Andalucía (FQM–195 and P11–FQM–7756). M. M.
thanks the MINECO for a predoctoral contract. M. A. R.–C.
thank MECD for a FPU scholarship Thanks are also extended to
the Ramón y Cajal Program (E. P. and J.–C. H.–G.). M. L.–H.
acknowledges the financial support from the Juan de la Cierva
Fellowships Program of MINECO (IJCI–2014–19367). M. M and
M. A. R.–C. have equally contributed to this work.
prone to saturate the cation, in contrast to H
2
, which should not
have a significant interaction. The calculated energy of activation
-1
a
(E ) for 3 (35 KJ mol ) is much lower than that of commercial
-
1
catalysts (E
a
≈ 65 KJ mol ), which opens the gate to perform the
0
reaction at lower temperatures with Pt
2
catalytic sites.
on Pt 0
may
In the present case, the dissociation of H
2
2
occur in two ways: 1) by metal–metal assisted hydrogen splitting,
as it occurs in extended metal surfaces, to form an intermediate
H–Pt–Pt–H species, or 2) by splitting in just one Pt atom, to give
a Pt–Pt(H)H intermediate. While the former intermediate nicely
Keywords: metal-organic frameworks • structural flexibility •
platinum • metal clusters • catalysis
explains the easy hydrogenation of CO
2
if hydrides attack to
external CO , the latter intermediate should not be discarded
2
since it can be formed prior to H–Pt–Pt–H species. Indeed,
computational calculations have suggested that the splitting of
[
[
1]
2]
A. M. Argo, J. F. Odzak, F. S. Lai, B. C. Gates, Nature 2002, 415, 623–
26.
6
H
2
onto an ideal Pt
not in two Pt atoms.
mechanisms where both
concomitantly activated on Pt
2
species is energetically favored on one but
J. Oliver-Meseguer, J. R. Cabrero-Antonino, I. Dominguez, A. Leyva-
Perez, A. Corma, Science 2012, 338, 1452–1455.
[38]
If so, Langmuir–Hinshelwood type
and second reactant are
in 3 would also be possible,
H
2
a
[3]
A. Corma, P. Concepción, M. Boronat, M. J. Sabater, J. Navas, M. J.
Yacaman, E. Larios, A. Posadas, M. A. López-Quintela, D. Buceta, et
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2
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COMMUNICATION
Entry for the Table of Contents
COMMUNICATION
Marta Mon, Miguel A. Rivero–Crespo,
Jesús Ferrando–Soria, Alejandro Vidal–
Moya, Mercedes Boronat, Antonio
Leyva–Pérez,* Avelino Corma,* Juan C.
Hernández–Garrido, Miguel López–
Haro, José J. Calvino, Giulio Ragazzon
Alberto Credi, Donatella Armentano*
and Emilio Pardo*
,
Page No. – Page No.
Synthesis of densely-packaged,
ultrasmall Pt0
clusters within a
2
thioether functionalised MOF and
their catalytic activity in industrial
reactions at low–temperature
We report the multigram synthesis of Pt0
MOF). The high stability and crystallinity of the selected MOF offers an
clusters within a metal-organic framework
2
(
unprecedented characterization of such ultrasmall entities. Finally, This novel hybrid
material catalyses, efficiently and at low temperature important industrial reactions
such as hydrogen cyanide (HCN) production, carbon dioxide (CO
and alkene hydrogenations.
2
) methanation
This article is protected by copyright. All rights reserved.