From Ru nanoparticle-encapsulated metal-organic frameworks to highly catalytically active Cu/Ru nanoparticle-embedded porous carbon

Article abstract of DOI:10.1039/c6ta10748f

A facile method for the in situ encapsulation of highly dispersed ultrafine Ru nanoparticles in HKUST-1, a copper-1,3,5-benzenetricarboxylate (BTC) metal-organic framework (MOF), without aggregation on the external surface of MOF crystallites has been developed. The thermal transformation of Ru@HKUST-1 composites in an inert atmosphere has yielded ultrafine Cu/Ru nanoparticle-embedded porous carbon, which shows very high catalytic activity and good durability for ammonia borane hydrolysis. During the thermal treatment of Ru@HKUST-1 composites, highly graphitic carbon formed around the Cu/Ru nanoparticles depressed the sintering of nanoparticles, resulting in the fine distribution of tiny nanoparticles in the carbon matrix. For the first time, the utilization of metal nanoparticle-encapsulated MOFs as a template/precursor for the synthesis of catalytically active metal nanoparticle-embedded porous carbon has been revealed.

Full text of DOI:10.1039/c6ta10748f

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ISSN 2050-7488
PAPER
Kun Chang, Zhaorong Chang et al.
Bubble-template-assisted synthesis of hollow fullerene-like
MoS2 nanocages as a lithium ion battery anode material
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DOI: 10.1039/C6TA10748F
PAPER
From Ru nanoparticle-encapsulated metal-organic framework to
highly catalytically active Cu/Ru nanoparticle-embedded porous
carbon
Received 00th January 20xx,
Accepted 00th January 20xx
Pradip Pachfule,a Xinchun Yang,a,b Qi-Long Zhu,a Nobuko Tsumori,c Takeyuki Uchida,a and Qiang
Xu*a,b
DOI: 10.1039/x0xx00000x
www.rsc.org/
A facile method for in situ encapsulation of highly dispersed nanocatalysts.3,4 Metal

organic frameworks (MOFs)5,6 have
ultrafine Ru nanoparticles in HKUST-1, copper1,3,5- been used as supports for effectively immobilizing metal
a
benzenetricarboxylate (BTC) metal-organic framework (MOF), nanoparticles inside pores by the nano-confinement effects,7-9
without aggregation on the external surface of MOF crystallites has while most of the MOFs have limited thermal and chemical
been developed. The thermal transformation of Ru@HKUST-1 stabilities. Therefore, it is highly desired to develop a
composites in an inert atmosphere has yielded the ultrafine Cu/Ru methodology to effectively immobilize metal nanoparticles with
nanoparticle-embedded porous carbon, which show very high controlled growth and high stability on stable supports. Herein,
catalytic activity and good durability for ammonia borane we have developed a novel strategy for the synthesis of highly
hydrolysis. During the thermal treatment of Ru@HKUST-1 dispersed Cu/Ru nanoparticle-embedded porous carbon
composites, highly graphitic carbon formed around the Cu/Ru composites using the Ru nanoparticle-encapsulated Cu-MOF
nanoparticles depressed the sintering of nanoparticles, resulting in composites, which have been synthesized by a facile one-pot in
the fine distribution of tiny nanoparticles in carbon matrix. For the situ method, as a self-dedicated template/precursor (Fig. 1).
first time, the utilization of metal nanoparticle-encapsulated MOFs The small sized Cu/Ru nanoparticle-embedded porous carbon
as a template/precursor for the synthesis of catalytically active materials exhibit significant catalytic activity, and in particular,
metal nanoparticle-embedded porous carbon has been revealed.
excellent durability for hydrolysis of ammonia borane (AB).10,11
The synthesis of microcrystalline Cu3(BTC)2 MOF (HKUST-
1)12 and the Ru@HKUST-1 composites (Ru@HKUST-1a, -1b and
-1c) with different contents of Ru was achieved by one-pot
solvothermal reaction of Cu(NO3)2.3H2O and RuCl3.xH2O with
BTC in an ethanol and N,N-dimethylformamide (DMF) mixture
at 85 C (Fig. 1; Table S1). During the solvothermal process, Ru
nanoparticles were uniformly encapsulated into the
octahedron-shaped HKUST-1 crystals (vide infra). The pyrolysis
Introduction
The Heterogeneous catalysis based on metal nanoparticle
catalysts is of paramount importance in many areas of the
chemical and energy industries due to their uncountable
applications.1,2 Supported monometallic and bimetallic
nanoparticles have been extensively applied as heterogeneous
catalysts, while they often suffer from particle aggregation
during the reaction process and thus a corresponding loss of
catalytic activity. So far, extensive efforts have been devoted for
resolving the stability issues of supported metal
of HKUST-1 or Ru@HKUST-1a, -1b and -1c at 800 C in an argon
atmosphere yielded porous carbon with stable and ultrafine Cu
or Cu/Ru nanoparticles embedded inside (Cu@C or Cu/Ru@C-
1a, -1b and -1c) through a morphology-preserved thermal
transformation process,13 as observed by scanning electron
microscopy (SEM) and transmission electron microscopy (TEM)
analyses (vide infra) (Fig. 2; Fig. S1-S4).
a.National Institute of Advanced Industrial Science and Technology (AIST), Ikeda,
Osaka 563-8577, Japan. Fax: +81-72-751-9629; Tel: +81-72-751-9562. *E-mail:
q.xu@aist.go.jp
b.Graduate School of Engineering, Kobe University, Nada Ku, Kobe, Hyogo 657-
8501, Japan.
Experimental
Materials: All the reagents and solvents used for the synthesis
were commercially available and used without further
purification. Copper (II) nitrate trihydrate (Cu(NO3)2.3H2O,
Sigma Aldrich, 98%), benzene-1,3,5-tricarboxylic acid (Sigma
Aldrich, 98 %), ruthenium(III) chloride n-hydrate (RuCl3.xH2O,
c. Toyama National College of Technology, Hongo-machi, Toyama 939-8630, Japan.
Electronic supplementary information (ESI) available: Materials, instrumentation
details, experimental details for the preparation of MOFs, Cu@C, Cu/Ru@C and
Ru@(Cu@C) composites, procedures for determination of catalytic activities,
additional SEM and TEM images, electron tomographic measurements, X-ray
diffraction, XPS, FTIR, TGA and other supporting data can be found in the Electronic
Supplementary Information. See DOI: 10.1039/x0xx00000x
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Wako Pure Chemical Industries, Ltd., 99%) and ammonia borane
(NH3BH3, JSC Aviabor, 97%) were used as received.
View Article Online
DOI: 10.1039/C6TA10748F
Fig. 1 (a) Schematic illustration of the synthesis of Ru@HKUST and Cu/Ru nanoparticle-embedded porous carbon composites for AB hydrolysis. (b) PXRD
patterns of HKUST-1, Ru@HKUST-1a, -1b and -1c, showing the matching profiles with the simulated HKUST-1 pattern. (c) N2 sorption analyses of HKUST-1,
Ru@HKUST-1a, -1b and -1c, showing the decrease in porosity with increasing loading of Ru nanoparticles. (d) N2 sorption analyses of Cu@C, Cu/Ru@C-1a, -1b
and -1c, showing the porosities of carbon composites. Closed and open symbols represent the adsorption and desorption branches, respectively.
Synthesis of Cu3-BTC2 MOF (HKUST-1): 1.16 g Cu(NO3)2.3H2O (4.84 boat and placed into a temperature-programmed furnace. The
mmol) was dissolved in 25 mL ethanol at 60 C. A solution of 0.491 g sample was heated slowly from room temperature to 800 C in 4 h
BTC (2.34 mmol) in 25 mL DMF was added under stirring and the
and then kept at 800 C for 3 h under flowing argon gas. The furnace
reaction mixture was refluxed for 6 h at 85 C. Then, the reaction was allowed to cool down to room temperature naturally in argon
mixture was transferred into a Teflon-lined autoclave and heated at atmosphere. The resultant brown coloured material of Cu@C or
Cu/Ru@C in 25-30 % yield was collected directly from the ceramic
boat and used without further purification.
85 C for 12 h. After cooling the autoclave to room temperature, the
obtained material was filtered and washed with DMF (3 x 25 mL) and
ethanol (3 x 25 mL). The sample was dried at 60 C for 6 h and 150 C
for 18 h under vacuum.
Synthesis of Ru@(Cu@C)-3.4 wt.% and Ru@(Cu@C)-9.4 wt.%: In the
typical syntheses, 0.100 g of as-synthesized Cu@C was dispersed in
5 mL of water/ethanol (2:1) solvent and the mixture was sonicated
for 10 min until it became homogeneous. After stirring for 30 min,
RuCl3.xH20 (6.96 mg for Ru@(Cu@C)-3.4 wt.%; 19.24 mg for
Ru@(Cu@C)-9.4 wt.%) dissolved in 2 ml distilled water was added
dropwise over a period of 5 min with constant vigorous stirring. The
resulting solution was continuously stirred for 60 min. The reduction
of Ru3+@(Cu@C) was carried out by adding 5 mL freshly prepared 1
M aqueous NaBH4 solution under vigorous stirring, resulting in the
generation of catalysts as a dark brown suspension. The synthesized
sample was collected by centrifuging, dried at 100 C under vacuum,
and used for the catalytic reactions.
Synthesis of Ru@HKUST: For the synthesis of Ru@HKUST-1a, 0.932
g Cu(NO3)2.3H2O (3.87 mmol) and 0.258 g RuCl3.xH2O (0.97 mmol)
were dissolved in 25 mL ethanol at 60 C. A solution of 0.491 g BTC
(2.34 mmol) in 25 mL DMF was added under stirring and the reaction
mixture was refluxed for 6 h at 85 C. Then, the reaction mixture was
transferred into a Teflon-lined autoclave and heated at 85 C for 12
h. After cooling the autoclave to room temperature, the obtained
material was filtered and washed with DMF (3 x 25 mL) and ethanol
(3 x 25 mL). The sample was dried at 60 C for 6 h and 150 C for 18
h under vacuum. The syntheses of Ru@HKUST-1b (0.990 g
Cu(NO3)2.3H2O (4.11 mmol) and 0.190 g RuCl3.xH2O (0.73 mmol)) and
Ru@HKUST-1c (1.05 g Cu(NO3)2.3H2O (4.35 mmol) and 0.130 g
RuCl3.xH2O (0.49 mmol)) were performed by following the same
procedure except using the different amounts of metal salts.
Catalytic hydrolysis of ammonia borane: The hydrolysis of ammonia
borane (NH3BH3, AB) can be briefly expressed as the formula:
NH3BH3 + 4H2O → NH4+ + B(OH)4- + 3H2
Synthesis of carbon composites: The activated sample of HKUST-1,
Ru@HKUST-1a, -1b or -1c (0.50 g) was transferred into a ceramic
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The activity of catalysts towards the hydrolysis of AB was determined
by measuring the rate of hydrogen evolution. The experimental
setup for measuring the hydrogen evolution from the
View Article Online
DOI: 10.1039/C6TA10748F
Fig. 2 (a) TEM image of Ru@HKUST-1b, showing the octahedron-shaped morphology of MOF crystals. (b, c) HAADF-STEM images of Ru@HKUST-1b, showing
the presence of highly dispersed and ultrafine Ru nanoparticles in the crystal matrix, without aggregation on outer surface. (d) Size histogram of Ru
nanoparticles in Ru@HKUST-1b. (e) TEM image of Cu/Ru@C-1b, showing the highly dispersed Cu/Ru nanoparticle-embedded porous carbon composites. (f, g)
HAADF-STEM images of Cu/Ru@C-1b, showing the ultrafine Cu/Ru nanoparticle-embedded porous carbon. (h) Size histogram of Cu/Ru nanoparticles in
Cu/Ru@C-1b.
aqueous AB solution is the same as previously reported.10a In inductively coupled plasma (ICP) analysis for Ru@HKUST-1b
general, a mixture of catalyst (50 mg) and distilled water (3 mL) confirmed the presence of Cu (21.2 wt.%) and Ru (3.4 wt.%)
was placed in a two-necked round-bottomed flask (30 mL), (Table S1). Thermogravimetric analyses (TGA) of HKUST-1,
which was placed in a water bath at room temperature under Ru@HKUST-1a, -1b and -1c in an argon atmosphere showed the
ambient atmosphere. A gas burette filled with water was thermal stabilities up to 250
connected to the reaction flask to measure the volume of The PXRD analyses of Cu@C, Cu/Ru@C-1a, -1b and -1c
hydrogen. The reaction started when aqueous AB solution (1 showed sharp peaks at 44, 51 and 74 , corresponding to the
C (Fig. S6).


mmol in 1 mL water) was injected into the mixture using a characteristic diffractions of Cu (cubic) (Fig. S7). In addition, the
syringe. The volume of the evolved hydrogen gas was less intense peaks in the PXRD profiles of Cu/Ru@C-1a, -1b and
monitored by recording the displacement of water in the gas -1c at
38, 42, 44, 58, 69 and 79 correspond to the
burette. The reaction was completed when there was no more characteristic diffractions of Ru (hcp). No additional peaks were
gas generation.
observed for metal oxides and other impurities in the carbon
matrix, in agreement with the X-ray photoelectron
spectroscopic (XPS) analyses (Fig. S8). The XPS investigation of
Cu/Ru@C-1b at the Cu 2p and Ru 3d levels confirmed the
Results and discussion
The powder X-ray diffraction (PXRD) profiles of Ru@HKUST-1a, presence of metallic Cu and Ru in the carbon matrix. Since
-1b and -1c match well with the corresponding diffractions of Raman ID/IG ratios (where ID and IG are the Raman intensities of
HKUST-1 synthesized by the similar method and the simulated D-band and G-band at 1325 and 
1590 cm−1, respectively) are
PXRD pattern of HKUST-1, indicating the high crystallinity and widely used to evaluate the degree of graphitization of carbon
the same structural integrity of Ru nanoparticle-encapsulated materials,14 we have performed Raman analyses for the as-
HKUST-1 (Fig. 1b).12 Moreover, no diffractions were detected synthesized samples of Cu@C, Cu/Ru@C-1a, -1b and -1c. As
for Ru nanoparticles in Ru@HKUST-1a, -1b and -1c, indicating shown in Fig. S7, the relative intensity (ID/IG) ratios for Cu@C,
the encapsulation of very small Ru nanoparticles in MOF matrix. Cu/Ru@C-1a, -1b and -1c are 1.00, 1.04, 0.97 and 0.96,
Further, the similar coordination environment in HKUST-1, respectively, which suggest the formation of highly graphitic
Ru@HKUST-1a, -1b and -1c has been verified using Fourier carbon during the pyrolysis of MOFs.15 With different Cu/Ru
transform infrared spectroscopy (FTIR) analyses (Fig. S5). The ratios in the starting materials of Ru@HKUST composites, the
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resulted Cu/Ru@C composites showed different Cu/Ru ratios, the thermal transformation of MOF to carbon composites (Fig.
View Article Online
as revealed by ICP analyses (Table S2).
S2). The TEM images of Cu/Ru@C-1b shoDwOtIh: 1e0.u10lt3r9a/fCin6TeAC10u7/4R8uF
The N2 sorption isotherms of HKUST-1 show a surface area nanoparticle-embedded porous carbon structures (Fig. 2e),
of 1762 m2g-1, close to the values previously reported (Fig. 1c).12 suggesting the expediency of octahedron-shaped MOF
As compared with pristine HKUST-1, the decrease in N2 uptake, nanostructures for the fabrication of porous carbon composites
Brunauer–Emmett–Teller (BET) surface area and pore volume through the morphology-preserved thermal transformation of
of the Ru@HKUST-1a, -1b and -1c samples indicates that the MOF precursor,13,17 without using polymer and other templates
cavities of the host frameworks are occupied and/or blocked by to control the damage of MOF morphology.18 The HRTEM and
the encapsulated Ru nanoparticles in MOF matrix (Fig. 1c, Fig. HAADF-STEM images of Cu/Ru@C-1b illustrate the formation of
S3 and S9, Table S1), as observed in the cases of loading metal tiny Cu/Ru nanoparticle (3-4 nm) embedded porous carbon
nanoparticles to MOF-5, ZIF-8 and other porous materials.8,9,16 structures (Fig. 2f-2h; Fig. S4). Additionally, the electron
As expected, the pore size distributions for HKUST-1, tomographic measurements demonstrate the uniform 3D
Ru@HKUST-1a, -1b and -1c calculated using non-local density distribution of the Cu/Ru nanoparticles throughout the carbon
functional theory (NLDFT) method confirm the formation of octahedron (Movie S1). It is reasonable to consider that during
micropores in MOF matrix (Fig. S9). The N2 sorption analyses of the prolonged heating (3 h) of Ru@HKUST-1b at 800 C, the
Cu@C, Cu/Ru@C-1a, -1b and -1c show typical type IV isotherms MOF crystallites were converted into carbon, ultrafine Cu/Ru
with the surface areas of 135, 92, 113 and 139 m2g-1, nanoparticles and other volatile products. We believe that
respectively (Fig. 1d). As calculated from N2 sorption isotherms, during the thermal treatment, highly graphitic carbon around
Cu@C, Cu/Ru@C-1a, -1b and -1c show both micro- and meso- the Cu/Ru nanoparticles depressed the sintering of Cu/Ru
pores (Fig. S9).
nanoparticles, resulting in the fine distribution of tiny
SEM analyses of HKUST-1, Ru@HKUST-1a, -1b and -1c show nanoparticles in carbon matrix,19 as observed in the HRTEM
the formation of micro-crystalline octahedra (Fig. S1). TEM images and Raman analysis of Cu/Ru@C-1b (Fig. S4 and S7).
analyses of Ru@HKUST-1b further confirm their octahedron-
It is well-known that ammonia borane is a promising
shaped morphology (Fig. 2a; Fig. S3). High-resolution TEM material for chemical hydrogen storage, from which hydrogen
(HRTEM) and high-angle annular dark field scanning TEM can be released through hydrolysis.10,11 We have evaluated the
(HAADF-STEM) images of Ru@HKUST-1b substantiate the catalytic activity of the Cu/Ru nanoparticle-embedded porous
encapsulation of Ru nanoparticles of an average size of 2-3 nm carbon composites for AB hydrolysis. The reaction was initiated
inside the MOF matrix (Fig. 2b-2d; Fig. S3). These HRTEM and by introducing aqueous AB solution into the reaction flask
HAADF-STEM images showed no aggregation of Ru containing the as-synthesized catalysts with vigorous shaking at
nanoparticles in the interior of MOF matrix as well as on the room temperature. H2 generated from the AB hydrolysis was
exterior surface of MOF crystals (Fig. S3).
collected in the burette, with which the H2 volume was
As observed in SEM analyses, Cu@C, Cu/Ru@C-1a, -1b and monitored. Fig. 3a shows the H2 generation using carbon
-1c preserve the parent MOF precursor morphology through composites Cu@C, Cu/Ru@C-1a, -1b and -1c with different
the thermal transformation of MOF to carbon composites (Fig. loadings of Cu and/or Cu/Ru (Table S2). It is revealed that
S2). The TEM images of Cu/Ru@C-1b show the ultrafine Cu/Ru Cu/Ru@C-1b is the most active for AB hydrolysis compared to
nanoparticle-embedded porous carbon structures (Fig. 2e), their counterparts, probably due to the fine distribution of
suggesting the expediency of octahedron-shaped MOF Cu/Ru nanoparticles in the porous carbon composite (Table S2).
nanostructures for the fabrication of porous carbon composites Interestingly, in the case of Cu/Ru@C-1b catalyst, AB hydrolysis
through the morphology-preserved thermal transformation of reaction is completed in 100 s (Ru/AB = 0.0465 in molar ratio)
MOF precursor,13,17 without using polymer and other templates with a 72 mL H2 release, corresponding to H2/AB = 3, giving a
to control the damage of MOF morphology.18 The HRTEM and turnover frequency (TOF) as high as 97 molH2·molcat-1·min−1
HAADF-STEM images of Cu/Ru@C-1b illustrate the formation of based on the amount of Ru (Fig. 3a). Further, the increased H2
tiny Cu/Ru nanoparticle (3-4 nm) embedded porous carbon release rates from the AB hydrolysis have been observed at
structures (Fig. 2f-2h; Fig. S4). Additionally, the electron elevated temperatures (Fig. 3b). The apparent activation energy
tomographic measurements demonstrate the uniform 3D (Ea) of this reaction over Cu/Ru@C-1b was estimated to be 39.2
distribution of the Cu/Ru nanoparticles throughout the carbon kJ mol−1 within the temperature range of 293−323 K (Fig. S10).
octahedron (Movie S1). It is reasonable to consider that during On the contrary, the Cu/Ru@C-1a and Cu/Ru@C-1c catalysts
the prolonged heating (3 h) of Ru@HKUST-1b at 800 C, the synthesized using a similar procedure, but having different Ru
MOF crystallites were converted into carbon, ultrafine Cu/Ru contents, show sluggish kinetics and lower TOFs for AB
nanoparticles and other volatile products. We believe that hydrolysis (Fig. 3a; Table S2).
during the thermal treatment, highly graphitic carbon around
It is found that the productivity of H2 over the Cu/Ru@C-1b
the Cu/Ru nanoparticles depressed the sintering of Cu/Ru catalyst almost remains unchanged for five runs, which can be
nanoparticles, resulting in the fine distribution of tiny attributed to the high stability and durability of metal
nanoparticles in carbon matrix,19 as observed in the HRTEM nanoparticle-embedded porous carbon (Fig. S14). The
images and Raman analysis of Cu/Ru@C-1b (Fig. S4 and S7).
recyclability of Cu/Ru@C-1b has been analysed by isolating the
As observed in SEM analyses, Cu@C, Cu/Ru@C-1a, -1b and catalyst after each successive cycle, and the catalytic activity
-1c preserve the parent MOF precursor morphology through remained almost unchanged over 4 cycles, suggesting the
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DOI: 10.1039/C6TA10748F
Fig. 3 a) Plots of time vs. volume of hydrogen generated from hydrolysis of AB (1 mmol) at 298 K catalyzed by the Cu@C, Cu/Ru@C-1a, -1b and -1c catalysts
(50 mg). Inset: the corresponding TOF values on the basis of Ru in the catalysts. b) Temperature dependent catalytic activity of Cu/Ru@C-1b for AB hydrolysis.
c) Recyclability test for the hydrogen generation from aqueous AB solution catalyzed by isolated Cu/Ru@C-1b after each successive cycle, showing almost
unchanged catalytic activity over 4 cycles.
Table 1. Comparative TOF and energy of activation observed for
Co35Pd65/C
22.7
66.2
97
27.5
11g
8b
CuRu@C-2 with literature reported materials.
AuNi@MIL-101_a
CuRu@C-1b
-
39.2
20.03
30.59
-
Energy of
TOF
(molH2.molcat
min−1)
This work
23c
activation
(kJ mol-1)
Catalyst
.
Reference
Ag@Co/graphene
Ru1Cu7.5/graphene
NiRu@MIL-101
Pd@Co/graphene
102.4
135
272
916
21b
RGO/Pd
Pd/zeolite
6
51
55.9 ± 2.2
67.0
46 ± 2
-
22a
22b
22c
22d
22e
22f
20c
22g
22h
22i
23d
6.2
-
23e
Ru/-Al2O3
23
Ru@Al2O3
39.6
45
durability of catalyst for AB hydrolysis (Fig. 3c). PXRD analyses
of Cu/Ru@C-1b after catalysis showed no significant change in
the diffraction patterns (Fig. S11). The high activity and good
durability of Cu/Ru@C-1b demonstrate the great potential of
Cu/Ru nanoparticle-embedded porous carbon composites for
AB hydrolysis. In addition, the catalytic activity of Cu/Ru@C-1b
is among the highest reported for the monometallic and
bimetallic catalysts (Table 1).10,11,20-23 In a control experiment,
the catalysts (Ru@(Cu@C)-3.4 and 9.4 wt.%) prepared by
supporting 3.4 and 9.4 wt.% of Ru onto the Cu@C composite
using conventional impregnation method showed much lower
catalytic activities and durabilities compared to Cu/Ru@C-1b
(Fig. S12 and S13), suggesting the importance of the use of in
situ synthesized Ru nanoparticle-encapsulated MOF (HKUST-1)
as the self-dedicated template/precursor for the preparation of
metal nanoparticle-embedded porous carbon composites. Also,
in additional blank experiment, we have synthesized Cu/Ru
nanoparticle-supported carbonaceous material by the direct
pyrolysis of the starting materials (RuCl3.xH2O, Cu(NO3)2.3H2O
and BTC linker) at 800 °C under argon atmosphere. The
ammonia borane hydrolysis studies carried out using as-
synthesized carbonaceous sample showed negligible catalytic
activity, signifying the importance of MOF template for the
preparation of active catalyst (Fig. S15). As HKUST-1 and
Ru@HKUST-1a, -1b and -1c are not stable in aqueous medium,
the feasibility of using them as catalysts for the hydrolysis of AB
Pd@MIL-101
Ru(0) nano-clusters
Ru/graphene
Ru(0)@X–NW
Ru(0)/HAp
75
47 ± 2.2
11.7
77
100
135
137
187
260.8
266.9
329
429.5
446.4
600
567
1350
10.7
33.0
66.3
58 ± 2
-
Ru@MIL-101
Ru@MIL-53(Cr)
Ru@MIL-53(Al)
Ru(0)@MWCNT
Ru/C
28.9
33.7
33 ± 2
34.81 ± 0.12
-
22j
22j
22k
22l
Pt@MIL-101 (Cr)
Ru/graphene
Pt/CNTs-O-HT
Rh0/CeO2
8a
12.7
-
20h
22m
22n
23a
23b
23b
43 ± 2
38
MCM-1@Cu0.2Ni0.8
RuCu/-Al2O3
RuCo/-Al2O3
52.0
47.0
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939–943; (d) S. Horike, S. Shimomura and S. Kitagawa, Nature
has been limited, as confirmed by the TEM and PXRD analyses
of the catalysts recovered after the first cycle (Fig. S16).
View Article Online
Chem. 2009, 1, 695–704; (e) H.-C. Zhou, J. R. Long and O. M.
DOI: 10.1039/C6TA10748F
Yaghi, Chem. Rev. 2012, 112, 673-674; (f) A. G. Slater and A. I.
Cooper, Science 2015, 348, 988; (g) Y. Bai, Y. Dou, L.-H. Xie, W.
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In summary, for the first time, a facile method for the
encapsulation of highly dispersed ultrafine Ru nanoparticles in
HKUST-1 has been achieved by solvothermal reaction of the
precursors. The thermal transformation of Ru nanoparticle-
encapsulated HKUST-1 composites under an inert atmosphere
yielded the ultrafine Cu/Ru nanoparticle-embedded porous
carbon composites, which exhibit extraordinary catalytic
activity for ammonia borane hydrolysis with good durability.
During the thermal treatment of Ru@HKUST-1 composites,
highly graphitic carbon around the Cu/Ru nanoparticles,
depressed the sintering of nanoparticles, resulting in the fine
distribution of tiny nanoparticles in carbon matrix. The novel
synthesis of highly active and stable metal nanoparticle-
embedded porous carbon composites from metal nanoparticle-
encapsulated MOFs may pave its future applications in catalytic
transformation reactions.
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Acknowledgements
The authors acknowledge Japan Society for the Promotion of
Science (JSPS) for financial support. P. P. thanks JSPS for
postdoctoral fellowship.
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Journal of Materials Chemistry A
Page 8 of 8
View Article Online
DOI: 10.1039/C6TA10748F
Journal of Materials Chemistry A
From Ru nanoparticle-encapsulated metal-organic framework to
highly catalytically active Cu/Ru nanoparticle-embedded porous
carbon
Graphical abstract
High−temperature pyrolysis of Ru nanoparticle-encapsulated MOF (Ru@HKUST-1)
afforded the ultrafine Cu/Ru nanoparticle-embedded porous carbon composites
(Cu/Ru@C), which show a high catalytic activity for ammonia borane hydrolysis.