Highly efficient hydrogenative ring-rearrangement of furanic aldehydes to cyclopentanone compounds catalyzed by noble metals/MIL-MOFs

Article abstract of DOI:10.1016/j.apcata.2019.02.023

Hydrogenative ring-rearrangement reaction of biomass-derived furanic aldehydes to cyclopentanone compounds catalyzed by metal/support bifunctional catalysts suffers a low selectivity of target product and serious carbon loss because of the Br?nsted acid catalysis. Herein, a series of pure Lewis acid sites MIL-MOFs (Fe-MIL-100, Fe-MIL-101 and Cr-MIL-101) with different crystal topology structures and metals are synthesized. Then the nanoparticles of Ru, Pt, Pd and Au are uniformly dispersed on the internal surface of the MOF support. The hydrogenation rate catalyzed by the noble metals/Fe-MIL-100 is three times faster than those obtained with Fe-MIL-101 and Cr-MIL-101-based catalysts due to the higher dispersion of nanoparticles on the former to make it more accessible to reactants. Meanwhile, both of the noble metals on Fe-MIL-100 and Fe-MIL-101 have a higher selectivity of cyclopentanone compounds than that on Cr-MIL-101, since the Fe ions in the MOF host with a higher oxophilicity will promote the adsorption and hydrolysis of the intermediate furanic alcohols (furfural alcohol or 2,5-bis(hydroxymethyl)furan). Furthermore, the noble metals/MIL-MOFs catalyst can maintain a good activity and stability after recycling for five runs. The current work will present an efficient catalytic reaction system for the hydrogenative ring-rearrangement of furfural and 5-hydroxymethyl furfural to synthesize cyclopentanone compounds.

Full text of DOI:10.1016/j.apcata.2019.02.023

Accepted Manuscript
Title: Highly efficient hydrogenative ring-rearrangement of
furanic aldehydes to cyclopentanone compounds catalyzed by
noble metals/MIL-MOFs
Authors: Xiang Li, Qiang Deng, Likang Zhang, Jun Wang,
Rong Wang, Zheling Zeng, Shuguang Deng
PII:
S0926-860X(19)30088-2
DOI:
Reference:
https://doi.org/10.1016/j.apcata.2019.02.023
APCATA 16993
To appear in:
Applied Catalysis A: General
Received date:
Revised date:
Accepted date:
27 November 2018
11 February 2019
16 February 2019
Please cite this article as: Li X, Deng Q, Zhang L, Wang J, Wang R, Zeng Z,
Deng S, Highly efficient hydrogenative ring-rearrangement of furanic aldehydes to
cyclopentanone compounds catalyzed by noble metals/MIL-MOFs, Applied Catalysis
A, General (2019), https://doi.org/10.1016/j.apcata.2019.02.023
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Highly efficient hydrogenative ring-rearrangement of furanic aldehydes to cyclopentanone
compounds catalyzed by noble metals/MIL-MOFs
a,b
a,b,
a,b
a,b
a,b
a,b
Xiang Li , Qiang Deng *, Likang Zhang , Jun Wang , Rong Wang , Zheling Zeng ,
Shuguang Denga,b,c,*
aKey Laboratory of Poyang Lake Environment and Resource Utilization, Nanchang University,
Ministry of Education, Nanchang 330031, PR China
bSchool of Resource, Environmental and Chemical Engineering, Nanchang University, Nanchang
3
30031, PR China
cSchool for Engineering of Matter, Transport and Energy, Arizona State University, 551 E. Tyler
Mall, Tempe, AZ 85287, USA
*Corresponding Author. E-mail: dengqiang@ncu.edu.cn (Qiang Deng); Shuguang.Deng@asu.edu
(Shuguang Deng).
Graphical Abstract
Highlights


Pd/Fe-MIL-100 shows higher activity of and selectivity than Cr-MIL-101
and Fe-MIL-101.



Pd-based catalysts is more active and selective than Ru, Pt and Au.
The catalysts are highly efficient for both furfural and 5-hydromethylfurfural.
The catalysts are stable and recyclable.
Abstract
Hydrogenative ring-rearrangement reaction of biomass-derived furanic aldehydes to
cyclopentanone compounds catalyzed by metal/support bifunctional catalysts suffers a low
selectivity of target product and serious carbon loss because of the Brønsted acid catalysis. Herein,
a series of pure Lewis acid sites MIL-MOFs (Fe-MIL-100, Fe-MIL-101 and Cr-MIL-101) with
different crystal topology structures and metals are synthesized. Then the nanoparticles of Ru, Pt,
Pd and Au are uniformly dispersed on the internal surface of the MOF support. The hydrogenation
rate catalyzed by the noble metals/Fe-MIL-100 is three times faster than those obtained with
Fe-MIL-101 and Cr-MIL-101-based catalysts due to the higher dispersion of nanoparticles on the
former to make it more accessible to reactants. Meanwhile, both of the noble metals on
Fe-MIL-100 and Fe-MIL-101 have a higher selectivity of cyclopentanone compounds than that on
Cr-MIL-101, since the Fe ions in the MOF host with a higher oxophilicity will promote the
adsorption and hydrolysis of the intermediate furanic alcohols (furfural alcohol or
2
,5-bis(hydroxymethyl)furan). Furthermore, the noble metals/MIL-MOFs catalyst can maintain a
good activity and stability after recycling for five runs. The current work will present an efficient
catalytic reaction system for the hydrogenative ring-rearrangement of furfural and
5
-hydroxymethyl furfural to synthesize cyclopentanone compounds.
Keywords: furanic aldehydes, noble metals/MIL-MOFs, hydrogenative ring-rearrangement,

cyclopentanone compounds, high-value chemicals.

1
. Introduction
Due to the fast depletion of fossil resource and great demand of chemicals, biomass is expected
to become an increasingly important feedstock for the production of valuable chemicals.[1] In
particular, the inedible lignocellulose is an important renewable alternative, because it can provide
furanic aldehydes (furfural or 5-hydroxymethyl furfural) after chemical conversions.[2,3] Furanic
aldehydes are considered as the prospective platform compounds, and can be converted into some
products such as furfuryl alcohol, 2,5-bis(hydroxymethyl)furan, cyclopentanone, 3-hydroxymethyl
cyclopentanone and so on.[4,5,6] Among them, cyclopentanone compounds (cyclopentanone or
3
-hydroxymethyl cyclopentanone) contain a five-membered ring and carbonyl group. A
multifunctional chemical intermediate has been widely utilized as a raw material to produce
pharmaceuticals, insecticides, rubber and high-density fuel.[7] Conventionally, the production of
cyclopentanone is mainly via cyclization of petroleum-derived adipic acid or adipic esters, and there
is no industrial synthesis path of the 3-hydroxymethyl cyclopentanone. Recently, to provide an
alternative path and extend the utilization of biomass, the production of cyclopentanone
compounds from furanic aldehydes has attracted a wide attention.
Numerous studies have demonstrated that the hydrogenative ring-rearrangement of furanic
aldehydes to cyclopentanone compounds can be catalyzed by the supported noble or non-noble
metals bifunctional catalysts under hydrogenation conditions. In the transformation process,
furanic aldehydes can be transformed to cyclopentanone compounds through several C=O
hydrogenation, furan ring hydrolysis, C=C hydrogenation, intramolecular aldol condensation and
dehydration reactions.[8] Although some efforts have been devoted to developing active
non-noble metals for hydrogenation steps, efficient catalyst acid supports for hydrolysis,
intramolecular aldol condensation, and dehydration steps still need to be studied.[9-12] For
example, carbon supported Pt, Ru, Pd-Cu and Ni catalysts have been found to be successful to
catalyze the reaction of furfural. [10,13-15] However, the reaction condition is comparatively
severe (160-190°C), since the hydrolysis is hardly occurred with a weak acidic support.[15]
Subsequently, some acidic metal oxides (such as TiO
molecular sieves (such as HY, HZSM-5 and SBA-15) have been used as the
support.[9,11-12,16-18] Whereas, a support with strong acidity (such as Ta and Nb ) is
2 3 4 2 3 2
, Co O , Al O and ZrO ) and acidic
2
O
5
2 5
O

needed for the 5-hydroxymethyl furfural reaction, since the hydrogenation intermediate
,5-bis(hydroxymethyl)furan has a electron withdrawing hydroxymethyl group and is hard to
2
hydrolyze.[19-21] Unfortunately, the synthesis efficiency is always unsatisfactory, because a large
amount of low-value humins are generated catalyzed by this kind of catalysts. It is found that
Lewis acid has a crucial effect in the reaction by promoting the hydrolysis and intramolecular
aldol condensation steps, whereas Brønsted acid easily promotes the intermolecular C-C reaction
of intermediates, leading to the production of humins.[22] The catalytic performance of these
traditional supports can be ascribed to the low density of Lewis acid sites and the existence of
Brønsted acid sites. Hence, developing a suitable support for the bifunctional catalyst is the key for
highly efficient synthesis of cyclopentanone compounds.
Recently, metal-organic frameworks (MOFs) with modular assembly structure, high surface
area, tailorable pore and structural versatility show a good application potential in the fields of gas
storage, separation, catalysis, sensing, drug delivery and proton conductivity.[23-28] In particular,
MIL-series MOFs with carboxylic-acid-based ligands, show a promise for the future application
owing to their greater chemical variety, better chemical stability and larger pore size.[29-31] These
MOF materials have been widely reported as heterogeneous catalysts on the basis of Lewis acid
sites, which are offered by unsaturated metal centers.[32] Moreover, the tuned cages or channels
allow them to host or support metal nanoparticles as an bifunctional catalyst by changing the
organic linkers. In fact, the stable and pure Lewis acid catalyst (Ru/Cr-MIL-101) has a
considerable yield in the furfural reaction. However, it cannot convert 5-hydroxymethyl furfural to
3
-hydroxymethyl cyclopentanone, since the acidity of the unsaturated coordination of Cr3+ in the
MOF is weak and it cannot induce the hydrolysis of furan ring.[33] According to previous reports,
the activity of MOF is usually tuned by the metal oxophilicity in many reactions involving
oxygen-containing compounds.[34-36] For example, Fe-based MOF with higher metal
oxophilicity always have a higher activity than Cr-based MOF, although their topology structures
are same. Meanwhile, the effect of noble metal types on the selectivity for the hydrogenation
ring-arrangement reactions have not been systematically explored.
Therefore, a series of noble metals (Pt, Ru, Pd and Au) supported on MIL series MOF with
metal and topology structure are synthesized via the impregnation method in this study. The role

of noble metal types as well as supports has been investigated respectively, and the reaction
conditions have been optimized. Attributed to the smaller particle size of Pd and higher
3
+
oxophilicity of Fe , the conversion rate of furfural and selectivity of cyclopentanone over
Pd/Fe-MIL-100 are higher than 99.0% and 93.1%, respectively. Moreover, it also has a high
activity for the conversion of 5-hydromethyl furfural, and the yield of 3-hydroxymethyl
cyclopentanone is 85.4%. M/MIL-MOF is very stable and performs steady with a little decrease in
the yield after 5 runs. It seems that the catalysis by MOFs will represent a promising route for the
bifunctional catalysis including the step of Lewis acid catalysis.
2
. Experimental section
2
.1 Materials
Furfural (99.5%), furfuryl alcohol (99%), tetrahydrofurfuryl alcohol (99%), cyclopentanone,
N,N-dimethyl formamide (DMF), ethanol, iron powder, chromium(III) nitrate nonahydrate
Cr(NO ·9H O), iron chloride hexahydrate (FeCl ·6H O), hydrofluoric acid (35 wt% HF), nitric
acid (65%, HNO ), terephthalic acid (H BDC), trimesic acid (H BTC) were purchased from
(
3
)
3
2
3
2
3
2
3
Sinopharm Chemical Reagent Company. 5-Hydroxymethyl furfural (99%) was obtained from
Beijing Coupling Technology Company. 2,5-Bis(hydroxymethyl)furan (98%) and 2,5-bis
(hydroxymethyl) tetrahydrofuran (95%) were supplied by Nanjing Aikang Chemical Company.
3
1
-Hydroxymethyl cyclopentanone was purchased from Hubei Jusheng Technology Company.
-Hydroxyl-2,5-hexanedione was obtained from Shanghai KaiShu Chemical Technology
Company. Chloride ruthenium (RuCl
acid hexahydrate (H PtCl ·6H O), palladium chloride (PdCl
2
3
), chlorauric acid trihydrate (HAuCl
4 2
·3H O), chloroplatinic
2
6
2
) were supplied by Sigma-Aldrich
Chemical Reagent Company. All chemicals were used without further purification. Cr-MIL-101
was synthesized according to our previous study.[7]
2
.2 Synthesis of catalysts
Fe-MIL-101 and Fe-MIL-100 were prepared by following the previously reported
3 2 2
procedures.[36-37] For the synthesis of MIL-101, FeCl ·6H O (2.45mmol) and H BDC (1.24
mmol) were dissolved in 30 ml DMF and heated at 110 °C for 20 h in a Teflon-lined autoclave.
The resulting brown solid was firstly filtered off and purified by using DMF, ethanol and water,
3
then dried overnight at 150 °C. For the synthesis of Fe-MIL-100, iron powder (4.9 mmol), H BTC

(3.27 mmol), hydrofluoric acid (4 mmol) and nitric acid (2.78 mmol) were mixed in water (20 ml),
and heated for 12 h at 150 °C. The synthesized Fe-MIL-100 was further purified with water and
ethanol, then dried overnight in a 100 °C vacuum drying oven.
M/MOF (M=Ru, Pt, Pd, Au) catalysts were prepared by the incipient-wetness impregnation
method. Typically, 1 g MIL-MOF
HAuCl ·3H O (the noble metal loading is 5 wt%) were added to 10 mL water. The mixture was
stirred for 2 h, and the pH of the solution was adjusted to 7, then 0.5 g of NaBH was added. The
stirring was continued for 30 min. The resultant solid catalyst was filtered and dried in an oven at
S 2 3 2 6 2
and 0.084 g PdCl / 0.103 g RuCl / 0.133 g H PtCl ·6H O/ 0.1g
4
2
4
1
00 °C. Before catalytic reaction, all MOF catalysts were activated in vacuum at 150 °C for 12 h.
.3 Catalyst characterizations
2
The crystal structures were characterized with powder X-ray diffraction (XRD) using a
Panalytical Empyrean diffractometer with Cu-Kα radiation. X-Ray photoemission spectroscopy
XPS) data were gained by an ESCALAB 250Xi instrument equipped with a monochromatic Al
anode X-ray gun. The pore textural properties were determined by N adsorption-desorption at
196 °C on an ASAP 2046 surface analyzer. The specific surface area and mesopore size
(
2
-
distribution were calculated by the BET and DFT methods, respectively. Fourier transform
infrared (FTIR) spectra was recorded in the range of 400-4000 cm-1 on a Nicolet 5700 FTIR
spectrometer using KBr pellets. Elemental analysis was carried out using Inductively Coupled
Plasma Optical Emission Spectrometry on a PerkinElmer Optima 8000 spectrometer. The
microstructure was obtained by a JEM-2100 transmission electron microscope. The thermal
2
stabilities were analyzed by TGA measurements on a NETZSCH-STA 2500 in N atmosphere.
Acid properties were analyzed by the infrared spectroscopy of adsorbed pyridine using a Bruker
2
VERTEX 70 spectrometer. For the IR analysis, self-supported wafers (10 mg/cm ) were degassed
for 1 h under vacuum at 200 °C, then the adsorption of pyridine proceeded at 60 °C for 30 mins
followed by desorption at 100 °C and 200 °C for 20 min, and the transmission spectra were
recorded.
2
.4 Catalytic reactions
In a typical experimental run, a mixture of furanic aldehydes (10.4 mmol), water (40 mL) and
.1 g catalyst was stirred in a 100 mL batch autoclave (Anhui Kemi Machinery Technology Co.,
0

2
LTD), then reacted under a specific temperature and H pressure. The mixture was periodically
sampled and a certain amount of N,N-dimethyl formamide was added as an internal standard
substance. Then, the products were extracted by ethyl acetate. The compositions were identified
by an Agilent 6890N GC/5973 MS detector and determined by Trace 1300 gas chromatograph
equipped with FID detector and a TG-WAXMS capillary column (30 m×0.32 mm×0.25 μm). The
reported data were the mean values of three trials with small error bars.
3
3
. Results and Discussion
.1 Structural characteristics of M/MIL-MOF
S
ICP analysis results show the content of noble metal in M/MIL-MOF
added content of noble metal precursor under the synthesis condition. Figure 1 shows the XRD
patterns of M/MIL-MOF . The characteristic peaks attributed to the MIL-MOF are all in
S
is consistent with the
S
S
accordance with the reported data in the literature, confirming that the successful formation of MIL
series MOF.[36-38] Cr-MIL-101 and Fe-MIL-101 have the same diffraction patterns, whereas
Fe-MIL-100 has a different one, indicating the space topology structure is not related to types of
metal ions, but to the ligand. Meanwhile, after the incorporation of noble metal nanoparticles, the
XRD pattern is matched well with both of noble metal nanoparticles and MOF. The diffraction
peaks located at 2θꢀ=ꢀ38.6°, 44.0° are assigned to the (100), (101) planes of the standard card of
Ru. The peaks at 39.7°, 46.2° are attributed to the (111), (200) planes of Pt. The characteristic
peaks of Pd (111), (200) planes are observed at 2θ = 40.1°, 46.6° and the Au (111), (200) planes
are located at 2θ = 38.5°, 44.8°. The integrity of the characteristic peaks of MIL-MOFs is retained
and it is not affected by the introduction of metal nanoparticles.[39-43]
As shown in Figure S1, the deconvolution of high resolution Ru 3p XPS spectrum of the
Ru/Fe-MIL-100 sample gives a distinctive peak at 463.6 and 485.7 eV that can readily be assigned
to Ru(0). The peak observed at 468 eV reveals the presence of Ru(IV) oxidation state on the metal
surface. For Pt/Fe-MIL-100, the stronger peaks at 71.1 eV and 74.6 eV for Pt 4f7/2 and Pt 4f5/2 are
belonged to metallic Pt(0). The other doublet at 72.3 eV and 75.8 eV could be assigned to Pt(II).
The binding energy peaks appear at 334.9 eV and 341 eV for Pd/MIL-MOFs, these peaks should
be attributed to Pd(0). In addition, two binding energy peaks at 338.5 eV and 344 eV are ascribed
to the 3d5/2 and 3d3/2 peaks of Pd(II). There are kinds peaks of Au species which could be

identified, Au(0) (84 eV, 87.7 eV) and Au(I) (86 eV, 88.8 eV).[39-42] Besides Pd, the amount of
oxidation states of other noble metals (Ru, Pt, Au) is very small. Although the amount of Pd(II) is
large, it is easily reduced to Pd(0) under subsequent reaction conditions (150 °C, 4 MPa H
2
).[14]
The N adsorption-desorption isotherms of MIL-MOFs and M/MIL-MOFs are identified,
2
which have the type IV isotherm and can be used to prove their mesoporous structures (Figure 2A,
2
B). The BET surface areas of Fe-MIL-101 and Cr-MIL-101 are 1708 and 3226 m /g, respectively.
The pore-size distribution centers at 1.17, 1.48, 2.16 and 2.73 nm in Figure 2C should be
corresponding to the two types of windows and cages of MIL-101. But Fe-MIL-100 has a more
2
compacted structure with BET surface areas of 841 m /g, and a smaller pore size distributed in
1
.72 and 2.16 nm. It should be corresponding to the two smaller topological cages of Fe-MIL-100
(Figure 2D).[7] After the introduction of nanoparticles, the specific surface area, pore volume and
pore size are substantially reduced for all samples. It is worth mentioning that the volume of same
cage and large cage (cage void) of all samples decrease equally with an increase in the introduced
amount of nanoparticles, indicating nanoparticles are evenly encapsulated in two types of cages
(Table 1).
TEM images and the particle size distributions of the M/Fe-MIL-100 (M=Ru, Pt, Pd, Au) are
shown in Figure 3. It clearly manifests that the noble metals clusters are uniformly dispersed in the
void cage of MOF. Meanwhile, the noble nanoparticles possess basic sizes with an average of 5-8
nm on the external surface of MOF. Pyridine-adsorbed FTIR spectra were widely used to probe the
-
1
acid sites (Figure S2). Generally, the wavenumber range in the 1400-1650 cm allow to determine
the Lewis acid strength. However, it is not accessible in the case of MILs-MOF due to the very
strong bands due to carboxylate and ring vibrations. Some adsorption peaks are observed at 1015,
-
1
1
1
044, and 1071 cm , which are assigned to the ν , ν12 and ν18a modes of the pyridine chemisorbed
on Lewis acid sites of MOF [44,45]. Notably, the area of these peaks is large for the sample treated
at 100 °C (Figure 4). However, at higher adsorption temperature (200 °C), the signal of Fe-based
catalysts is higher than that of Cr-based, showing a stronger Lewis acidity of coordinated
3
+
unsaturated Fe .
As shown in Figure S3, the thermal stability data of the Fe-MIL-100 and Fe-MIL-101 shows
the weight loss below 200°C can be attributed to the removal of crystal and non-crystal water.

Subsequently, the significant weight loss of Fe-MIL-100 and Fe-MIL-101 are observed from 300
to 500 °C owing to the decomposition of ligands. The MOF catalysts retain their structure at
3
00 °C, indicating that they have a great stability under the hydrogenative ring-rearrangement
reaction conditions.
3
.2 Hydrogenative ring-rearrangement of furfural to cyclopentanone
As aforementioned, furfural (FFA) is sequentially converted to furfuryl alcohol (FA),
-pentene-1,4-dione (PED), 4-hydroxy-2-cyclopentenone (HCPEO), 3-hydroxycyclopentanone
2
(HCPO) and cyclopentanone (CPO) via hydrogenation, hydrolysis, intramolecular aldol
condensation, dehydration and hydrogenation reactions. These products were identified by
GC-MS (Figures S4 A-D). Beside these compounds, these reactions can generate some
by-products including tetrahydrofurfuryl alcohol (THFA) and humins through furan ring
hydrogenation and intermolecular C-C reactions, respectively (Figure 4A). Figures S5 compares
the concentration of reactants, intermediates and products with reaction time over Pd/Cr-MIL-101,
Pd/Fe-MIL-101 and Pd/Fe-MIL-100 under the same reaction condition. Over all catalysts, the
concentration of HCPEO and HCPO, PED are difficult to be detected, indicating the dehydration
and hydrogenation occurr very quickly. A large amount of FFA and FA indicates the C=O
hydrogenation and hydrolysis reactions are the controllable steps. Different from previous studies
on supports including BrØnsted acid, all samples with pure Lewis acid MOF show a lower than
2
.0% selectivity for humins.[15-21]
Although Pd/Fe-MIL-100 has the lowest surface area, it has three advantages on activity and
selectivity compared with Pd/Fe-MIL-101 and Pd/Cr-MIL-101. Firstly, it shows 99% conversion
of FFA after 6 h, which is higher than those over Pd/Fe-MIL-101 (63.0%) and Pd/Cr-MIL-101
(60.5%). Secondly, the hydrolysis ability for FFA is strong and the selectivity of CPO is 93.1%
after 6 h, which is quite higher than that of Pd/Cr-MIL-101 (71.2%). Thirdly, the formation of
THFA is completely inhibited with a selectivity of 1.7% due to a low concentration of
intermediate FFA. As a result, Pd/Fe-MIL-100 shows the highest yield of 92.2% for CPO (Figure
5
).
To further elaborate the excellent performance of Pd/MIL-100, kinetic studies on the
hydrogenation step of FFA and hydrolysis step of FA are carried out. It is found that the plot of

0
ln(C/C ) of FFA vs. time is a straight line, which reveals the hydrogenation step of FFA is followed
by the quasi first-order kinetics (Figure 4B). The kinetic parameters over Pd/Fe-MIL-100 are
obviously higher than those over Pd/Fe-MIL-101 and Pd/Cr-MIL-101. Because a more compacted
structure of MOF will promote the introduction of smaller Pd nanoparticles, which will enable the
accessibility of FFA to the hydrogenation active sites. For the hydrolysis study, the reaction is
conducted without hydrogen in order to eliminate the influence of furan ring hydrogenation.
Fe-MIL-101 and Pd/Fe-MIL-101 has the higher kinetic parameters than Fe-MIL-100 and
Pd/Fe-MIL-100, since their larger surface area can increase the accessibility of acid sites to FA.
Whereas Cr-MIL-101 and Pd/Cr-MIL-101 have a weak hydrolysis performance, because the
unsaturated Cr3+ has a weaker oxophilicity than Fe3+ (Figure 4C). The acid site adsorbing the
oxygen atom is the key step for the hydrolysis of furan alcohol and a better oxophilicity acid site
will be benefit for this step. These results clearly demonstrate that the excellent catalytic efficiency
of Pd/MIL-100 can be ascribed to the highest hydrogenation activity and the considerable
hydrolysis activity.
Subsequently, several other noble metals (Ru, Pt, Pd and Au) supported on Fe-MIL-100 are
investigated. As the widely recognized effectiveness of these metals in hydrogenation reactions,
Ru, Pt, Pd catalysts possess a high conversion of 97.8%, 98.1%, and 99.0% for FFA, respectively,
which are all higher than the conversion of 91.3% over Au catalyst (as shown in Figure 5).[46]
However, it is interesting to find that the Ru/Fe-MIL-100 and Pt/Fe-MIL-100 only show a small
selectivity for CPO (36.2% and 20.1%) and a large amount of intermediates FA (61.8% and
7
3.9%), despite that their specific surface areas are much larger than that of Pd/Fe-MIL-100 and
Au/Fe-MIL-100 (Figure 2D). The hydrolysis step of FA kinetic studies indicate that the
introduction of nanoparticles will decrease the activity of Fe-MIL-100. Because the solvent is
water and the interaction of water with noble metals may affect the hydrolysis activity. In previous
report, it is found that the adsorption energy of water on noble metals are in the orders of Rh >
Ru > Pt > Pd > Au,[47] which is consistent with the results of hydrolysis reaction in this study.
The adsorption on noble metals may restrain water react with FA on the Lewis acid site and reduce
the hydrolysis activity. The results show that Pd/Fe-MIL-100 has a high hydrogenation and
considerable hydrolysis activity, which indicates that it has the best comprehensive performance.

At last, the reaction conditions such as the loading amount of Pd, reaction temperature and H
2
pressure are optimized. The activity is increased with the amount of Pd active sites, however,
when the loading amount of Pd is further increased to 6 wt%, it will incur the hydrogenation of
furan ring. Thus, the 5wt%Pd/Fe-MIL-100 sample shows the highest catalytic yield of CPO
(Figure S6). When the reaction temperature is decreased to 130 °C, only 30% of FFA is
transformed, while the main product is FA and no CPO is detected. However, when the reaction
temperature is higher than 160 °C, the yield of CPO begins to decrease, and some products and
derivatives of intermolecular aldol condensation reaction of CPO are generated at high
2
temperatures.[7,8] (Figure S7) An increase in H pressure can lead to an enhancement in FFA
conversion. However, a higher selectivity to over-hydrogenated THFA is observed at H
2
pressures
over 4.0 MPa (Figure S8).
3
.3 Hydrogenative ring-rearrangement of 5-hydroxymethyl furfural to 3-hydroxymethyl
cyclopentanone
Similar to furfural, hydrogenative ring-rearrangement of 5-hydroxymethyl furfural (HMF) is
considered to proceed through C=O hydrogenation, hydrolysis, C=C hydrogenation,
intramolecular aldol condensation, dehydration and C=C hydrogenation reactions (Figure 6A
Figures S4 E-H). The product distribution is also measured in the HMF hydrogenative
ring-rearrangement reaction using Pd/Fe-MIL-100 as
-Hydroxy-3-hexene-2,5-dione (HHED) and 4-hydroxy-4-hydroxymethyl-2-cyclopentanone
HHCPN) are not detected, indicating that the reaction steps are very fast. Compared with the
a
catalyst (Figure 6B).
1
(
furfural conversion, it is notable that more than 20.8% yield of 1-hydroxyl-2,5-hexanedione (HHD)
is detected after 12 h, since the hydroxymethyl group can transfer electron to the carbonyl group.
It will decrease the positive charge carbocation from HHD and reduce the reactivity of
intramolecular aldol condensation reaction.[48] Figure S9 compares the time-dependent product
distribution of Pd/Cr-MIL-101, Pd/Fe-MIL-101 and Pd/Fe-MIL-100. Pd supported on
Cr-MIL-101 and Fe-MIL-101 have a lower activity than that of Fe-MIL-100 based on its low
dispersion of Pd nanoparticles. More importantly, Cr-MIL-101 cannot convert the hydrolysis of
2
2
,5-bis(hydroxymethyl)furan (BHF), and
a
large amount of hydrogenation product
,5-bis(hydroxymethyl)tetrahydrofuran (THBHF) is generated. Conversely, Fe-MIL-100 and

Fe-MIL-101 with a strong oxophilicity show a high hydrolysis activity. The BHF is rapid
consumed and the amount of byproduct THBHF is decreased.
All noble metals (Ru, Pt, Pd and Au) supported on Fe-MIL-100 show a high activity on the
hydrogenation reactions with above 80% conversion of HMF after 12 h. Meanwhile, due to the
weak hydrolysis activity of Ru and Pt catalyst, about 30% yield of BHF is maintained, and above
5
% yield of hydrogenation by-product THBHF is generated. While Pd and Au catalysts can
completely prevent the side reaction, and they have high hydrolysis performance with selectivity
of HCPN higher than 60%. At last, the yields of HHD and HCPN can increase to 20.2% and
7
5.6% after reacting 12 h, respectively. For a prolong reaction time to 24 h, the conversion over
Pd/Fe-MIL-100 is 99.9% with the 85.5% selectivity for HCPN.
3
.4 Catalyst stability and recycling
A rapid, hot-catalyst filtration test is performed (Figure S10). After the removal of
Pd/Fe-MIL-100, no further conversion of FFA and FA in the filtrate demonstrates the true
heterogeneous catalysis and suggests the stability of noble particles and MOF, respectively.
Meanwhile, the recycling of Pd/Fe-MIL-100 is further evaluated in the hydrogenative
ring-rearrangement of furfural. The catalyst is centrifuged after the reaction, washed with water,
and then used for the next run. As shown in Figure 7, after 5 runs, the conversion and selectivity
are maintained above 90% in the five runs, no significant decrease is found in conversion yield as
2
compared to the first reaction run. The XRD, FTIR and N adsorption results of the used catalysts
suggest the structure of the used catalysts basically be remained and has not change after five
reaction runs (Figure S11, S12, S13). TEM and ICP analysis results show the stable
chemical composition and no further agglomeration of Pd (Figure S14, Table S1). There is a great
proof that Pd/Fe-MIL-100 can be used as a stable catalyst under the present reaction conditions.
4
. Conclusions
Noble metal nanoparticles have been uniformly supported on MIL-MOFs with different spatial
configurations and different MOF coordination metals. Among the supports and noble metal
discussed in this work, the Pd/Fe-MIL-100 catalyst with a higher oxophilicity and small
nanoparticles dispersion shows the high activity of hydrogenation of furanic aldehydes and
hydrolysis of furan ring steps. Moreover, the reaction conditions are optimized. As a result, a

complete conversion of FFA and 92.2% yield of cyclopentanone is obtained at 150 °C and after 6
h. Meanwhile, hydrogenative ring-rearrangement of 5-hydroxymethyl furfural over
Pd/Fe-MIL-100, a conversion rate of 99.9%, and a 85.4% selectivity of 3-hydroxymethyl
cyclopentanone were achieved at 150 °C and after 24 h. In addition, the catalysts are easily
recyclable and without any obvious noble metals leaching and MOF structure degradation. The
outcomes in this study can contribute to the development of the biomass-derived cyclopentanone
compounds for a sustainable future.
Acknowledgements
The authors appreciate the supports from the National Natural Science Foundation of China
(
21878138, 21666021, 21706112), Natural Science Foundation of Jiangxi Province
20171BAB213017) and Postdoctoral Science Foundation of China (2017M622104,
(
2
018T110660) and the start-up funds from Nanchang University and Arizona State University..

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Cr-MIL-101
Pd
Pd
Pd/Cr-MIL-101
Fe-MIL-101
Pd/Fe-MIL-101
Fe-MIL-100
Ru
Ru/Fe-MIL-100
Pt
Pt/Fe-MIL-100
Pd/Fe-MIL-100
Au/Fe-MIL-100
Pd
Au
5
10 15 20 25 30 35 40 45 50 55 60 65 70
()
2
S
Figure 1. X-ray diffraction patterns MIL-MOF and M/MIL-MOFS.

1
200
400
300
200
100
0
B
A
Cr-MIL-101
Pd/Cr-MIL-101
Fe-MIL-101
9
6
3
00
00
00
0
Fe-MIL-100
Pd/Fe-MIL-101
Ru/Fe-MIL-100
Pt/Fe-MIL-100
Pd/Fe-MIL-100
Au/Fe-MIL-100
0.0
0.2
0.4
0.6
0.8
1.0
0
.0
0.2
0.4
0.6
0.8
1.0
P/P0
P/P0
C2.5
D 0.4
Cr-MIL-101
Fe-MIL-100
Pd/Cr-MIL-101
Fe-MIL-101
Pd/Fe-MIL-101
Ru/Fe-MIL-100
Pt/Fe-MIL-100
Pd/Fe-MIL-100
Au/Fe-MIL-100
2.0
1.5
1.0
0.5
0.0
0.3
0.2
0.1
0.0
1.0
1.5
2.0
2.5
3.0
3.5
1.0
1.5
2.0
2.5
3.0
3.5
Pore size (nm)
adsorption isotherms of and (C, D) pore-size distribution of MIL-MOF
and M/Fe-MIL-100 (M=Ru, Pt, Pd, Au).
Pore size (nm)
Figure 2. (A, B) N
2
S
,
Pd/MIL-MOF
S

Figure 3. TEM micrographs of (A)Pd/Cr-MIL-101, (B) Pd/Fe-MIL-101, (C) Ru/Fe-MIL-100, (D)
Pt/Fe-MIL-100, (E) Au/Fe-MIL-100 (F, G, H) Pd/Fe-MIL-100.

0
1
2
3
4
5
C 0
B
-1
-2
-3
-
-
-
-
-
Pd/Cr-MIL-101
Pd/Fe-MIL-101
Ru/Fe-MIL-100
Pt/Fe-MIL-100
Pd/Fe-MIL-100
Au/Fe-MIL-100
Fe-MIL-100
Pd/Cr-MIL-101
Pd/Fe-MIL-101
Ru/Fe-MIL-100
Pt/Fe-MIL-100
Pd/Fe-MIL-100
Au/Fe-MIL-100
Fe-MIL-100
Pd/Cr-MIL-100
Pd/Fe -MIL-101
Ru/Fe -MIL-100
Pt/Fe -MIL-100
Pd/Fe -MIL-100
Au/Fe -MIL-100
Pd/Cr-MIL-100
Pd/Fe -MIL-101
Ru/Fe -MIL-100
Pt/Fe -MIL-100
Pd/Fe -MIL-100
Au/Fe -MIL-100
-4
-5
0
1
2
3
4
5
6
0
1
2
3
4
5
6
t (h)
t (h)
Figure 4. The reaction pathway scheme (A); The kinetic experiments for the hydrogenation step
of FFA (B) and hydrolysis step of FA (C). Reaction conditions: (B) FFA (10.4 mmol), catalyst 0.1
g, water (40 mL), temperature 150 °C, 4.0 MPa H
2
; (C) FA (10.4 mmol), catalyst 0.1 g, water (40
mL), temperature 150 °C. C: concentration of FFA and FA.

FFA
CPO
FA
THFA
Humin
1
00
8
6
4
2
0
0
0
0
0
1
1
0
0
0
0
L-10
L-10
L-10
L-10
L-10
L-10
/
Cr-MI /Fe-MI
Pd
/
Fe-MI
/Fe-MI
/Fe-MI
Pd
Ru
Pt/Fe-MI Pd
Au
Figure 5. Hydrogenative ring-rearrangement of FFA to CPO over M/MIL-MOFs. Reaction
conditions: FFA (10.4 mmol), catalyst 0.1 g, water (40 mL), temperature 150 °C, 4.0 MPa H , time
h.
2
6

HMF
HHD
HCPN
THBHF
BHF
Humin
B
1
00
8
6
4
2
0
0
0
0
0
a
L-101
L-101
L-100
L-100
L-100
L-100
L-100
e-MI
/F
Pd
e-MI
Ru/F
e-MI
/F
Pt
e-MI
/F
Pd
e-MI
/
Cr-MI
e-MI
/F
Pd
Pd
Au/F
Figure 6. The reaction pathway scheme (A) hydrogenative ring-rearrangement of HMF to HCPN
over M/MIL-MOFs catalysts. Reaction conditions: HMF (10.4 mmol), catalyst 0.1 g, water (40
a
mL), temperature 150 °C, 4.0 MPa H
2
, time 12 h. Pd/Fe-MIL-100 catalyst: 24 h reaction time.

FFA
CPO
1
00
8
6
4
2
0
0
0
0
0
1
2
3
4
5
Recycle times
Figure 7. Recycling performance of the Pd/Fe-MIL-100 in furfural hydrogenative
ring-rearrangement. Reaction conditions: FFA (10.4 mmol), Pd/Fe-MIL-100 (0.1 g), water (40
2
mL), temperature 150 °C,4.0 MPa H , time 6 h.

Table 1. Physicochemical properties of synthesized catalysts.
S
BET
Pore Volume Volume of small cage
Volume of large cage
noble metal content
measured (wt%)
Samples
2
3
3
3
(
m /g)
(cm /g)
(cm /g)
(cm /g)
Cr-MIL-101
Pd/Cr-MIL-101
Fe-MIL-101
3226
1850
1708
1212
841
1.54
0.94
0.82
0.59
0.54
0.13
0.11
0.10
0.079
0.51
0.29
0.34
0.14
–
4.90
–
0.24
0.23
Pd/Fe-MIL-101
Fe-MIL-100
0.18
0.16
4.87
–
0.21
0.16
Ru/Fe-MIL-100
Pt/Fe-MIL-100
Pd/Fe-MIL-100
Au/Fe-MIL-100
143
0.056
0.049
0.043
0.038
0.036
0.033
0.028
0.024
4.78
4.89
5.01
4.96
130
123
87