One-pot synthesis and characterization of a dual-function hierarchical multiporous composite H3PW12O40?HKUST-1/γ-Al2O3 with enhanced performance in adsorptive desulfurization and acid catalysis

Article abstract of DOI:10.1080/00958972.2020.1790536

A hierarchical multiporous ternary composite HPW?HKUST-1/γ-Al₂O₃ (HPW = phosphotungstic acid) is prepared, in which the nanosized HPW?HKUST-1 is formed on both the external and internal surface of mesoporous γ-Al₂O₃ beads due to the confinement effect of internal pores/channels of the γ-Al₂O₃ beads. The composite not only possesses excellent adsorptive desulfurization capacity (e.g. 65.3 mg S/g MOF for dibenzothiophene; the adsorption capacities decreased in the order of dibenzothiophene > benzothiophene > 3-methylthiophene > 4,6-dimethyldibenzothiophene) superior to HKUST-1/γ-Al₂O₃ beads due to the significant role of the favorable acid-base interaction between acidic HPW and slightly basic sulfur-containing compounds, but also exhibits super acid catalytic activity for hydrolysis of ethyl acetate (325.6 mmol mol_acid^?1min^?1) and for synthesis of ethyl acetate (75.4 mol mol_acid^?1min^?1) and n-butyl acetate (13.2 mol mol_acid^?1min^?1) with selectivity of 100%, due to high dispersion and free access of the HPW in the composite which features high surface area and more easily accessible active sites of HPW and HKUST-1. Besides, the composite features remarkable mechanical strength, chemical/thermal stability, being friendly to the environment, and low cost, can easily be regenerated and reused many times for both acid catalysis reactions and adsorptive desulfurization without observable HPW leaching or material dissolution/decomposition.

Full text of DOI:10.1080/00958972.2020.1790536

Journal of Coordination Chemistry
ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/gcoo20
One-pot synthesis and characterization of a dual-
function hierarchical multiporous composite
H PW O @HKUST-1/γ-Al O with enhanced
3
12 40
2 3
performance in adsorptive desulfurization and
acid catalysis
Libo Qin , Yang Zheng , Zipeng Zhao , Yunshan Zhou , Lijuan Zhang , Zareen
Zuhra , Fang Tang & Chao Li
To cite this article: Libo Qin , Yang Zheng , Zipeng Zhao , Yunshan Zhou , Lijuan Zhang ,
Zareen Zuhra , Fang Tang & Chao Li (2020): One-pot synthesis and characterization of a dual-
function hierarchical multiporous composite H PW O @HKUST-1/γ-Al O with enhanced
3
12 40
2
3
performance in adsorptive desulfurization and acid catalysis, Journal of Coordination Chemistry,
DOI: 10.1080/00958972.2020.1790536
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JOURNAL OF COORDINATION CHEMISTRY
https://doi.org/10.1080/00958972.2020.1790536
One-pot synthesis and characterization of a dual-function
hierarchical multiporous composite H PW O @HKUST-1/
3
12 40
c-Al O with enhanced performance in adsorptive
2
3
desulfurization and acid catalysis
a,b
a
a
a
a
Libo Qin , Yang Zheng , Zipeng Zhao , Yunshan Zhou , Lijuan Zhang , Zareen
a
a
a
Zuhra , Fang Tang and Chao Li
a
State Key laboratory of Chemical Resource Engineering, College of Chemistry, Beijing University of
b
Chemical Technology, Beijing, P. R. China; Department of Chemistry, Changzhi University, Changzhi,
P. R. China
ABSTRACT
ARTICLE HISTORY
Received 21 April 2020
Accepted 1 June 2020
A hierarchical multiporous ternary composite HPW@HKUST-1/c-Al O
2
3
(
HPW ¼ phosphotungstic acid) is prepared, in which the nanosized
HPW@HKUST-1 is formed on both the external and internal surface
KEYWORDS
of mesoporous c-Al O3 beads due to the confinement effect of
2
Heteropoly acid; hierarchical
multiporous composite;
desulfurization; catalysis
internal pores/channels of the c-Al
only possesses excellent adsorptive desulfurization capacity (e.g.
5.3 mg S/g MOF for dibenzothiophene; the adsorption capacities
decreased in the order of dibenzothiophene > benzothiophene > 3-
methylthiophene 4,6-dimethyldibenzothiophene) superior to
HKUST-1/c-Al beads due to the significant role of the favorable
2 3
O beads. The composite not
6
>
2 3
O
acid-base interaction between acidic HPW and slightly basic sulfur-
containing compounds, but also exhibits super acid catalytic activity
ꢀ
1
ꢀ1
for hydrolysis of ethyl acetate (325.6 mmol molacid min ) and for
ꢀ
1
ꢀ1
synthesis of ethyl acetate (75.4 mol mol
min ) and n-butyl
acid
ꢀ
1
ꢀ1
acetate (13.2 mol molacid min ) with selectivity of 100%, due to
high dispersion and free access of the HPW in the composite which
features high surface area and more easily accessible active sites of
HPW and HKUST-1. Besides, the composite features remarkable
mechanical strength, chemical/thermal stability, being friendly to
the environment, and low cost, can easily be regenerated and
reused many times for both acid catalysis reactions and adsorptive
desulfurization without observable HPW leaching or material dissol-
ution/decomposition.
CONTACT Yunshan Zhou
Engineering, College of Chemistry, Beijing University of Chemical Technology, Beijing 100029, P. R. China; L.
Zhang ljzhang@mail.buct.edu.cn State Key Laboratory of Chemical Resource Engineering, College of
zhouys@mail.buct.edu.cn
State Key Laboratory of Chemical Resource
Chemistry, Beijing University of Chemical Technology, Beijing 100029, P. R. China
Supplemental data for this article is available online at https://doi.org/10.1080/00958972.2020.1790536.
ß 2020 Informa UK Limited, trading as Taylor & Francis Group

2
L. QIN ET AL.
1. Introduction
Polyoxometalates (POMs) owing to excellent chemical stability, super acidity, extraor-
dinary redox performance, and other remarkable features [1–3] have attracted increas-
ing attention for many catalyzed organic transformations and industrial applications
[3–9]. For example, as homogeneous catalysts, POMs are applied for the epoxidation
of olefins [8, 9], hydration of alkenes and esterification [4–6]. The experimental results
showed that the molar catalytic activities of POMs in organic media are usually
1
00–1000 times higher than that of H SO [6], meantime POMs do not enter into side
2 4
reactions by virtue of the inertness of the anion with organic reagents such as sulfon-
ation, chlorination, nitration, etc., that occur in the presence of mineral acids [6].
Although the homogeneous catalyzed reactions by POMs show high activity/selectiv-
ity, are friendly to the environment, and have mild operating conditions, they have
very high solubility in polar solvents, such as water, lower alcohols and ketones, etc.
that lead to difficulty for separation and recycling, while pure solid POMs have surface
2
ꢀ1
areas less than 10 m g [4] which limits their catalytic activity in practical applica-
tions due to less exposed active sites. Thus, it is necessary to disperse POMs on sup-
ports possessing high surface areas to increase recovery, recycling, and catalytic
performance.
Metal-organic frameworks (MOFs), a new type of porous crystalline material with
periodic multidimensional networks, are composed of a central metal and organic
ligands through covalent-bonding. MOFs possess wide potential applications in
adsorption [10], separation [11], catalysis [12], etc. in contrast to active carbon, sili-
cates, and zeolites [10–12] owing to the high specific surface area and rich surface
chemistry via varying the type of organic ligands and active metal sites. Especially,
MOFs are investigated as sulfur absorbers at mild environmental conditions, demon-
strating that MOFs possess excellent desulfurization capability with high selectivity as
compared to traditional adsorbents [13–20]. In addition, the notable extra-large pore
cavities in some MOFs enable them to encapsulate nano-sized POM clusters [21–26].
The resulting composite POM@MOFs do not merely improve the adsorptive desulfur-
ization performance for Lewis base compounds by acid-base interactions, such as
organosulfurs [23], but also overcome generally the drawbacks such as low quantity of
loading, leaching, irregular active centers, aggregation, and the deactivation of acid
sites encountered in the case of dispersion of POMs on traditional supports, such as
silica [27], active carbon [28], TiO2 [29], and zeolites [30]. However, the following

JOURNAL OF COORDINATION CHEMISTRY
3
tiresome problems exist in the POM@MOFs composite: MOFs have low thermal stabil-
ity due to their low coordination bond energy, thus MOFs cannot be used in high
temperature water and other harsh conditions because the coordination bonds can
partially or wholly crack. Usually, the outer surface of powdered POM@MOFs are
assessable by smaller molecules, but the inner pores/surface and the POMs therein are
not assessable to others, leading to low utilization of pore volume, surface area of
MOFs and active sites of the POMs therein. The mechanical strengths of POM@MOF
materials are usually poor, limiting recovery and recycling in industrial operation.
In this work, on the basis of the above consideration, the Keggin-type phospho-
tungstic acid (denoted HPW) which has been explored for different types of catalysis
due to their advantageous properties, and the rigid metal carboxylate HKUST-1 which
possesses stable framework, are deliberately integrated by using a simple one-step
hydrothermal technique on the surface of the millimeter-sized mesoporous c-Al O3
2
beads with numerous advantages, such as fine pore structure [31, 32], high specific
surface area, low price, and excellent chemical stability [33], through interactions
between hydroxyl groups of the carrier and carboxylic groups of the organic ligand
1,3,5-benzenetricarboxylic acid [34, 35]. Importantly, the resulting composite
POM@MOFs/c-Al O exhibits both superior adsorptive desulfurization and excellence
2
3
in the hydrolysis of ethyl acetate, synthesis of ethyl acetate and n-butyl acetate, due
to the confined environment of nano-sized channels/pores of c-Al O beads which can
2
3
effectively avoid aggregation of MOFs and the rich mesoporous structure of c-Al O3
2
beads which can decrease the mass transfer resistance and enhance the diffusion rate
of reactants, can be conveniently separated, recovered and recycled attributed to its
enhanced mechanical strength and millimeter size, therefore has great potentials in
industrial applications.
2
. Experimental
.1. Materials and methods
c-Al O beads were homemade by the State Key Laboratory of Chemical Resource
2
2
3
Engineering (Beijing University of Chemical Technology, China) and were washed three
ꢁ
times with distilled water and pre-treated at 200 C for 2 h before use. All other
reagents and solvents were commercially available and used as received. HKUST-1 and
HKUST-1/c-Al O were prepared following literature procedures [36].
2
3
The Fourier transform infrared (FT-IR) spectroscopy was carried on a Nicolet FTIR-
70SX spectrometer with mixed powdered materials and KBr pellets from 400 to
000 cm . Ultraviolet–visible spectroscopy (UV-vis) was recorded on a UV-2500 spec-
1
4
ꢀ
1
trophotometer to estimate the leakage of Keggin POM species by monitoring the
characteristic adsorption at 260-270 nm. Powder X-ray diffraction (XRD) data were
recorded on a Rigaku D/max 2500 X-ray diffractometer using graphite-monochromatic
ꢁ
ꢁ
ꢁ
Cu Ka radiation (k ¼ 0.15405 nm) from 2h of 5 to 70 with a scanning rate of 10 /min.
Scanning electron microscope (SEM) images and energy dispersive X-ray (EDX) map-
ping data were collected on a Zeiss Supra55 scanning electron microscope at an accel-
erating voltage of 20 kV. High Resolution Transmission Electron Microscopy (HRTEM)
images were obtained using a JEOL JEM2100 transmission electron microscope at an

4
L. QIN ET AL.
accelerating voltage of 200 kV. Elemental analyses were recorded on a Perkin-Elmer
40 C analytical instrument for C, H, N and the SPECTRO ARCOS type inductively
2
coupled plasma spectrometer (ICP) for Al, Cu. Thermogravimetric Analysis-Differential
Thermal Analysis (TG-DTA) curves were carried out using a Netzsch STA449 analyzer
ꢁ
ꢁ
ꢁ
ꢀ1
from 25 C to 800 C with a rate of 10 C min under air flow. The NH temperature-
3
programmed desorption (NH -TPD) was carried out on an Autochem 2920. Samples
3
ꢁ
ꢁ
ꢀ1
were first pre-treated at 300 C at a ramp rate of 10 C min in helium flow for 1 h
ꢁ
and then cooled to 40 C. Ammonia (10% NH /He) was introduced at a flow rate of
3
ꢀ
1
ꢁ
ꢁ
3
0 mL min for 1 h at 40 C and then blown by helium for 1 h at 40 C; the reactor
ꢁ
ꢁ
ꢀ1
temperature was increased to 600 C at a ramp rate of 10 C min , and the amount
of ammonia in effluent was measured. The nitrogen adsorption and desorption iso-
therms were carried out on an ASAP-2020 at 77 K. The specific surface area (SBET) was
determined from the linear part of the BET equation at a relative pressure of 0.05-0.3.
The pore size distribution was calculated using the Barrett-Joyner-Halenda method.
The total pore volume was determined from the amount of nitrogen adsorbed at a
relative pressure of ca. 0.99. The mechanical strength of the sample was measured on
a YHKC-2A particle strength tester. High performance liquid chromatography (HPLC)
equipped with a C18 column (length 250 mm, diameter 4.6 mm, diameter of filler
5
lm) was used for the quantitative assay of sulfur content. The mobile phase changed
from 10% water and 90% methanol gradient elution to 100% methanol in 10 min with
ꢀ
1
flow rate of 1.0 mL min . The ester contents were analyzed by a SP-6890 GC instru-
ment with a PEG-20M capillary column and n-tridecane was used as internal standard.
The GC operating conditions were as follows: the temperatures for injector and
ꢁ
ꢁ
ꢁ
detector were 240 C and 220 C, respectively, and the oven temperature was pro-
ꢁ
ꢁ
ꢀ1
ꢁ
grammed from 50 C (hold for 0.5 min) to 60 C at 2 C min , then raised to 150 C
ꢁ
ꢀ1
ꢁ
(
hold for 2.5 min) at 2 C min for ethyl acetate and from 60 to 150 C (hold for
.5 min) at 20 C min for n-butyl acetate.
ꢁ
ꢀ1
3
2
.2. Preparation of the composite material HPW@HKUST-1/c-Al O
2 3
In a typical synthesis, Cu(NO ) ꢂ3H O (1.8 mM), H BTC (1.0 mM) and HPW (0.04 mM)
3
2
2
3
were added into the H O:ethanol (V:V ¼ 1:1) solution (50 mL) and stirred magnetically
2
for 20 min at room temperature. Then the mixture and c-Al O beads (1.0 g) were
2
3
ꢁ
loaded in an autoclave (100 mL) and heated at 110 C for 20 h. After the reaction, the
autoclave was cooled to room temperature, the products were recovered by decanting
and washing three times with deionized water (10 mL). The obtained composite was
ꢁ
dried at 150 C overnight to remove water and other contaminants and then stored in
vacuum. The loading of HPW and HKUST-1 on the basis of elemental analysis (Al
3
8.82, Cu 5.02, C 5.70, P 0.11, W 7.21, and H 0.36%) are 9.4 and 17.3 wt% in the com-
posite, respectively.
2
.3. Adsorptive desulfurization
The model oil of S-containing compounds (dibenzothiophene (DBT), benzothiophene
BT), 3-methylthiophene (3-MT), 4,6-dimethyldibenzothiophene (4,6-DMDBT)) (250, 500
(

JOURNAL OF COORDINATION CHEMISTRY
5
and 1000 ppmw ) was prepared by dissolving S-containing compounds in n-octane,
S
which were used directly in the following adsorptive experiments. The model oil was
mixed with the adsorbent into a conical flask using a water bath under stirring at
atmospheric pressure, and the adsorptive performance was tested by HPLC. After the
adsorption, the HPW@HKUST-1/c-Al O was separated by decantation, washed with
2
3
acetone overnight to remove adsorbed S-containing compounds by using a Soxhlet
ꢁ
extractor and then dried at 150 C overnight in the oven. The performance of the
regenerated composite was tested as the fresh. The adsorptive desulfurization capacity
of the adsorbents was calculated by
W
M
Qi ¼ ðC0 ꢀ CiÞ ꢃ 10ꢀ
3
(1)
ꢀ
1
where Q is the adsorptive desulfurization capacity of the adsorbents (mg S g MOF);
i
W and M are the mass of model oil (g) and the absorber added (g), respectively; C0
and C are the initial and final sulfur concentrations in the model oil (ppmw ),
i
S
respectively.
2.4. Hydrolysis of ethyl acetate
Hydrolysis of ethyl acetate was carried out using 0.20 g HPW@HKUST-1/c-Al O3 as
2
catalyst with 5 wt% ethyl acetate aqueous solution (40 mL) in a 150-mL three-neck
flask with a Teflon stirrer, a water cooler condenser, and a thermometer (scheme S1,
ꢁ
supplementary material). The reaction temperature was raised immediately to 65 C
with controlled conditions using an oil bath under stirring for 2 h. After the reaction,
the catalyst was separated by decantation, washed three times with deionized water
ꢁ
(
10 mL) and then dried at 150 C overnight in the oven for the next recycling experi-
ments. The catalytic activity of HPW@HKUST-1/c-Al O for the hydrolysis of ethyl acet-
2
3
ate was estimated by conversion of ethyl acetate at 2 h and normalized by the unit
ꢀ
1
ꢀ1
ꢀ1
min ) and catalyst amount (k , mmol mol
acid.
ꢀ1
time (k , mmol g
min ). The k1
1
cat.
2
and k could be calculated by
2
k1 ¼ ðCNÞ=ðtmcatÞ
(2)
(3)
k ¼ k =acid amount
2
1
where C, N, t and mcat are the conversion of ethyl acetate, the molar amount of ethyl
acetate added (mmol), the reaction time (min), and the weight of the HPW@HKUST-1/
c-Al O (g), respectively.
2
3
2.5. Synthesis of ethyl acetate and n-butyl acetate
2.5.1. Synthesis of ethyl acetate
The synthesis of ethyl acetate was carried out using 0.6 mol of glacial acetic acid and
0
.3 mol of absolute ethyl alcohol in a 100-mL three-neck flask with a thermometer, a
Teflon stirrer, and a glass tube arranged by a water cooled condenser and a connect-
ing glass tube to collect the product (Scheme S2). The catalyst (0.10–0.35 g) was added
ꢁ
when the reaction temperature was raised to 75 C to initiate the reaction.

6
L. QIN ET AL.
Figure 1. IR spectra of the c-Al O beads (a), the composite (b), HPW (c) and HKUST-1 (d).
2
3
ꢄ
Symbols D and highlight the characteristic vibration bands from HKUST-1 and HPW, respectively.
2
.5.2. Synthesis of n-butyl acetate
The synthesis of n-butyl acetate was carried out using 0.6 mol of glacial acetic acid,
.3 mol of n-butyl alcohol, and 15 mL of toluene as water-carrying reagent in a 150-mL
three-neck flask with a Teflon stirrer, a thermometer, and a water segregator added 4/
0
5
volume of distilled water arranged by a water cooled condenser (scheme S3). The
ꢁ
reaction temperature was raised to 110 C and then the HPW@HKUST-1/c-Al O as
2
3
catalyst (0.20–0.50 g) was added to initiate the reaction.
The reaction temperature of the systems for the synthesis of ethyl acetate and n-
butyl acetate was controlled by an oil bath under stirring. After the reaction, the
ꢁ
catalyst was separated by decantation, washed with water and then dried at 150 C
overnight in the oven in order to do the next recycling experiments. The catalytic
activity of the HPW@HKUST-1/c-Al O for the synthesis of ethyl acetate and n-butyl
2
3
acetate was estimated from the conversion of alcohols calculated according to the
change in amount of ethyl and butyl alcohol by
Â
Ã
Xester ¼ ðmi–mtÞ=mi ꢃ 100%
(4)
where Xester, m and m represent the conversion of alcohol, the initial amount of alco-
i
t
hol (unit: g) and the amount of alcohol (unit: g) at a given time.
3. Results and discussion
3
.1. Characterization of the composite HPW@HKUST-1/c-Al O
2
3
Comparing IR spectra of the composite HPW@HKUST-1/c-Al O with that of c-Al O
2 3
2
3
support, HPW and HKUST-1 (Figure 1) showed characteristic vibration bands of the
ꢀ
1
ꢀ1
composite at 1084 cm , 894 cm from the P-O and W-O -W of HPW [37], bands at
b

JOURNAL OF COORDINATION CHEMISTRY
7
Figure 2. SEM images of the external surface of c-Al O (a), external (b) and inner cross-sectional
2
3
(
c) surface of the composite. The photographs of the c-Al O beads (a), the composite (b (over-
2 3
view), c (inner cross-section)) are also shown as insets highlighting color change from white to
blue. The EDX mapping of W (in green) (d) and Cu (in red) (e) of cross-section of the composite,
SEM-EDX cross-sectional line scans of W (f), and HRTEM images of the cross-section of the compos-
ite highlighting the lattice fringe (g, h). [Inset: highlighting the spherical appearance and color
change from white to blue].

8
L. QIN ET AL.
Figure 3. XRD patterns of the simulated c-Al O beads (a), the prepared c-Al O beads (b), HPW
2
3
2 3
(c), HKUST-1 (d), and the composite (e).
ꢀ
1
ꢀ1
ꢀ1
ꢀ1
1
650 cm (m
), 1564 cm (m
), 1457 cm (m
) and 1379 cm (d ) from
C¼O
asCOO
sCOO
ꢀ1
C–H
ꢀ1
ꢀ
1
HKUST-1 [38] and bands at 3455 cm (mO–H), 1632 cm (dH–O–H) [39], 950 cm (mAlO6
and 450 cm (dAlO6) [40] from c-Al O support. The results indicate that the compos-
)
ꢀ
1
2
3
ite HPW@HKUST-1/c-Al O was synthesized by loading HPW and HKUST-1 with their
2
3
original structures in the c-Al O support, further confirmed by the elemental analysis
2
3
3-
data (P:W ¼ 1:11.44 corresponding to the formula of PW O ; the loading amount of
12 40
HPW is calculated to be 9.4%) as well.
The observed color change from white for c-Al O beads (Figure 2(a)) to preserved
2
3
duck eggs-like blue for the composite (Figure 2(b,c)) further confirm the HPW@HKUST-
1
2
loading on c-Al O beads. Apart from above, there is no visible size change (Figure
2 3
(a,b): insert) observed with respect to their diameter (ca. 2 mm) between the c-Al O3
2
and the composite. To study distribution of the HPW and HKUST-1 of the composite,
the beads were sliced into equal parts for cross-sectional EDX mapping. It can be
clearly found that HPW and HKUST-1 are distributed uniformly in sub-micrometer
scales within the c-Al O beads (Figure 2(d,e)). W (tungsten) penetration depth in the
2
3
composite beads was more than 445 lm (Figure 2(f)), i.e. HPW@HKUST-1 penetration
depth is about half of the diameter of the composite. Moreover, another substantial
evidence for loading of the HKUST-1 on c-Al O beads is the presence of the lattice
2
3
fringe distance of 0.2297 nm corresponding to (880) crystal surface of HKUST-1 (Figure
2
2
(g)). According to the discontinuously lattice diffraction fringes of HKUST-1 (Figure
(h)), it can be speculated that discontinuous nanoparticles of HKUST-1 are formed/
deposited on the inner surface of pores/channels within c-Al O beads due to fast
2
3
nucleation of HKUST-1. In addition, the XRD pattern of the composite (Figure 3) shows
ꢁ
the relatively strong peaks at 2h values about 46.6 and 66.7 corresponding to (400)
and (440) reflections of c-Al O (JCPDS 10-0425) [41]. The appearance of a few weak
2
3
ꢁ
ꢁ
ꢁ
peaks at 2h values in 7.3 , 9.6 , and 13.7 (the gray dashed lines) are ascribed to the

JOURNAL OF COORDINATION CHEMISTRY
9
Figure 4. Low-temperature nitrogen adsorption-desorption isotherms of c-Al O beads (in black)
2
3
and the composite (in red). Inset is pore size distribution of c-Al O beads and the composite.
2
3
formation of nano-sized HKUST-1 of the composite [38] that is consistent with the
TEM and SEM results. The characteristic peaks of HPW phase (PDF#50-0657) does not
appear in the composite in the high-angle region indicating the high dispersion of
HPW in the composite [42].
The N adsorption isotherm of the composite (Figure 4) reveals a combination of
2
the typical I and IV type isotherms [43, 44], corresponding to the presence of both the
microporous and mesoporous structures, confirming formation of a hierarchical multi-
porous composite. Meanwhile, the hysteresis loops of the composite are superposition
of H1 type and H3 type representative of tubular capillaries and parallel slit shaped
pores that are caused by the granular particles of HPW@HKUST-1 that is confirmed by
2
the results of HRTEM [44]. The BET surface area for the composite (354.6 m /g) is larger
2
than that of carrier c-Al O beads (216.5 m /g), and the pore volume changes from
2
3
3
3
0
.68 cm /g for c-Al O to 0.386 cm /g for the composite (Table 1), due to the HKUST-1
occupying inner spaces of c-Al O bead has large BET surface area of 1601.4 m /g. For
2 3
2
2
3
comparison, it should be pointed out that the BET surface area for the composite
2
2
(
354.6 m /g) is larger than that of HKUST-1/c-Al O (320.1 m /g), while the pore vol-
2 3
3
ume for the composite (0.39 cm /g) is a little bit smaller than that of HKUST-1/c-Al O
2
3
3
(
0.40 cm /g) because of the contribution coming from HPW molecule of about 1 nm in
diameter with high surface area and spatial volume. The comparison of pore size dis-
tributions of c-Al O and the composite (Figure 4, inset) shows decreases in mean
2
3
pore size of 13.9 nm for c-Al O to broader region of 3 ꢅ 12 nm for the composite. The
2
3
composite shows a sharp peak of pore diameter (3.9 nm) followed by a broader one
reflecting the behavior of confinement-effect exertive internal pores/channels of
c-Al O bead on anchoring HPW@HUST-1 nanoparticles with penetration depth being
2
3
almost half of the diameter of c-Al O3 beads, as shown by the EDX mapping
2
(Figure 2(f)).

1
0
L. QIN ET AL.
Table 1. Texture of c-Al O , HKUST-1, HKUST-1/c-Al O and the composite.
2
3
2 3
Pore size of
maximum
possibility (nm)
Mechanical
strength
(N/grain)
Pore volume
(cm /g)
2
3
Samples
c-Al
S
BET (m /g)
HKUST-1 (%)
HPW (%)
9.4
2
O
3
216.5
1601.4
320.1
0.68
0.79
0.40
0.39
13.9
0.6
5.1
62.2
HKUST-1
HKUST-1/c-Al
2
O
3
18.7
17.3
96.1
99.5
HPW@HKUST-1/c-Al
2
O
3
354.6
8.7
Figure 5. NH -TPD profiles of HKUST-1/c-Al O (a) and the composite (b).
3
2 3
Figure 5 shows the NH -TPD profiles of HKUST-1/c-Al O and the composite. Three
3
2 3
ꢁ
ꢁ
ꢁ
main NH desorption peaks about 190 C, 467 C and 532 C are detected, correspond-
3
ing to desorption of NH from weak, middle and strong acid sites, respectively [45,
3
ꢁ
4
6]. Compared to the NH -TPD curve of HKUST-1/c-Al O , a peak at 532 C for the
3
2 3
composite could be assigned to NH that strongly adsorbed on the Brønsted acid sites
3
of HPW [47]. According to the desorbed amount of NH , the total acid amount
3
increases from 6.16 mmol/g for HKUST-1/c-Al O to 7.20 mmol/g for the composite.
2
3
The HPW has 97.9 lmol/g(HPW) of acidic protons corresponding with three acidic pro-
tons per polyanion calculated by the loading amount of HPW (9.4%). Considering the
fact that HPW can only stay inside type A pores of HKUST-1 [48] and the ratio of Cu/
P/W determined by ICP analysis is 48:2.2:23.8, it is concluded that nearly half of type A
pores of HKUST-1 are occupied with HPW in the composite.
Remarkably, the composite not only has enhanced thermal stability as compared to
ꢁ
ꢁ
HKUST-1 (decomposition temperature 505 C for the composite vs. 488 C for HKUST-
ꢁ
1
/c-Al O and 316 C for HKUST-1) (Figure S1, supplementary material) because of the
2
3
formation of the secondary bonding, such as Van der Waals interactions or hydrogen
bonds with the support [34, 35], but also enhanced mechanical strength (62.2 N/grain
for c-Al O and 99.5 N/grain for the composite) (Table 1). The composite has other
2
3
advantages such as low price, impact resistance, crush resistance, abrasion resistance

JOURNAL OF COORDINATION CHEMISTRY
11
Figure 6. Effect of time on adsorptive desulfurization capacity of c-Al O (a), HKUST-1 (b), HKUST-
2
3
1
/c-Al O (c), and the composite (d) for DBT at optimum reaction conditions.
2 3
and low coefficient of friction. All these merits are important and guarantee the poten-
tial of the composite for practical application.
3.2. Study on adsorptive desulfurization performance
The reduction of sulfur-containing compounds in commercial gasoline and diesel fuels is
a major concern of automotive and power generation industries [49, 50]. Among many
desulfurization technologies, adsorptive desulfurization attracts extensive attention owing
to advantages such as low cost, mild operation conditions and no requirement of hydro-
gen. MOFs showed superior adsorption capacities in contrast traditional adsorbents due
to the porous structure and extraordinary specific surface area [49, 50]. The composite
HKUST-1/c-Al O that we previously reported showed higher desulfurization performance,
2
3
especially with convenience in separation, recovery, and recycling [36], however, the
composite still has low pore utilization and desulfurization selectivity.
The optimum reaction time (Figure 6, Figure S2, 60 min; supplementary material),
ꢁ
reaction temperature (Figure S3, 30 C; supplementary material), and mass ratio of oil
to HKUST-1 (Figure S4, m(oil)/m(HKUST-1; supplementary material) ¼ 40:1) are investi-
gated in this work. As shown in Figure 6, the adsorptive desulfurization capacity and
adsorption rate of HPW@HKUST-1/c-Al O are higher than those of c-Al O , HKUST-1
2
3
2 3
and HKUST-1/c-Al O , indicating efficient utilization of the surfaces/pores in the com-
2
3
posite HPW@HKUST-1/c-Al O ; the corresponding adsorptive desulfurization rate is
2
3
reduced over time because the DBT concentration around adsorbent molecules
decreases. Specifically, the adsorptive desulfurization capacity for HPW@HKUST-1/
ꢀ
1
c-Al O at optimum reaction conditions is 65.3 mg S g MOF. There is significant
2
3
ꢀ
1
increase of 9.4% in the desulfurization efficiency compared to 59.7 mg S g MOF for
HKUST-1/c-Al O . According to the dynamic diameter of the DBT molecule (5.97 Å),
2
3
2
the dynamic molecular size of the DBT molecule (0.26 nm ), and BET surface area of
the HKUST-1 (1601 m /g), it can be calculated that the DBT molecules occupy 19.9% of
2
total surface area of HPW@HKUST-1/c-Al O . The surface area utilization dramatically
2
3
increased by 9.3% compared to 18.2% for HKUST-1/c-Al O . The fact that the surface
2
3

1
2
L. QIN ET AL.
Table 2. Comparison of adsorptive desulfurization capacity of reported adsorbents and the com-
posite for DBT.
Adsorbent
Solvent
C
0
(ppmw
S
) / system
Q
0
(mg S/g MOF)
28.9
MIL-101 [23]
Cr-BDC [15]
Cr-BTC [15]
n-octane
n-octane
n-octane
iso-octane
iso-octane
ꢅ714/batch
1000/batch
1000/batch
300/fixed bed
300/fixed bed
300/fixed bed
300/fixed bed
300/fixed bed
300/fixed bed
<160/batch
<174/batch
<261/batch
<261/batch
<174/batch
300/batch
c
41.0
30.7
c
MOF-5 [50]
12.7
20.5
66.3
9.1
MOF-505 [50]
UMCM-150 [50]
MOF-5 [50]
MOF-505 [50]
UMCM-150 [50]
ZIF-8-derived [51]
ZIF-8-derived [51]
CMK-3 [52]
CMK-5 [52]
Activated Al
Activated carbon [54]
Carbon aerogel [55]
Cu(I)-Y zeolite [56]
iso-octane
iso-octane:toluene (85:15)
iso-octane:toluene (85:15)
iso-octane:toluene (85:15)
n-hexane
n-hexane:para-xylene (9:1)
n-hexane
14.9
66.6
26.7
22.2
10.9
21.7
21.0
28.9
15.1
32.6
29.4
17.6
65-115
22.2
n-hexane
n-hexane
n-octane
n-hexadecane
n-octane
n-octane
n-octane
n-hexane
n-octane
2
O
3
[53]
<696/batch
ꢅ690/batch
ꢅ690/batch
<124/batch
178/batch
Co-Y zeolite [56]
Activated carbon spheres [57]
AC loaded Na, Co, Ag or Cu [58]
Ce/Ni-Y zeolite [59]
a
ꢅ124/batch
b
c
PT-Ag-MASN [60]
n-decane
500/batch
15.0
MC-Z(Cu, Co or Fe) [61]
HKUST-1 [36]
n-hexane
n-octane
n-octane
n-octane
178/batch
51.4-75.5
c
1000/batch
1000/batch
1000/batch
59.6, 49.5
76.1, 59.7
c
HKUST-1/c-Al2
O
3
[36]
c
HPW@HKUST-1/c-Al
2
O
3
84.7, 65.3
a
Mesoporous carbons with dispersed metal.
b
Mesoporous aluminosilicate nanoparticle with dispersed Ag.
c
Equilibrium adsorption.
2
3
area and pore volume are 320.12 m /g and 0.403 cm /g for HKUST-1/c-Al O , and
2
3
2
3
3
54.60 m g and 0.386 cm /g for the composite, respectively, indicate slight increase in
/
surface area and slightly decrease in pore volume after the incorporation of HPW into
HKUST-1/c-Al O . This means that the enhancement in the adsorptive desulfurization
2
3
capacity and adsorption rate for the composite, compared with HKUST-1/c-Al O , can-
2
3
not be simply explained with the porosity. In order to understand the role of the HPW
in the adsorptive desulfurization, a control experiment was done by using
NaPW@HKUST-1/c-Al O where sodium phosphotungstate (NaPW) was used to replace
2
3
HPW. The adsorptive desulfurization performance of NaPW@HKUST-1/c-Al O was tested
2
3
ꢀ
1
at same optimum reaction conditions and the adsorptive capacity was 38.2 mg S g
MOF, which was much lower than 65.3 mg S g MOF of HPW@HKUST-1/c-Al O and
even lower than 49.5 mg S g MOF of HKUST-1 and 59.7mg S g MOF of HKUST-1/
ꢀ
1
2
3
ꢀ
1
ꢀ1
c-Al O . The NaPW is thought to just occupy the pores of HKUST-1 leading to the inferior
2
3
adsorptive desulfurization capacity of NaPW@HKUST-1/c-Al O . In turn this result proves
2
3
the significant roles of Brønsted acidic centers of HPW in HPW@HKUST-1/c-Al O for
2
3
adsorptive desulfurization. It is clear that the introduction of HPW not only enhances
adsorptive desulfurization capacity, but also increases the adsorptive desulfurization
selectivity due to the acid-base interaction between acidic HPW and slightly basic sulfur-
containing compounds. Impressively, the composite HPW@HKUST-1/c-Al O3 showed
2
superior adsorptive desulfurization compared to reported adsorbents, such as traditional
zeolites, activated carbons, and MOFs listed in Table 2.

JOURNAL OF COORDINATION CHEMISTRY
13
Table 3. Pseudo-second-order rate constants (k ) of HKUST-1/c-Al O and the composite with
2
2 3
various DBT concentrations. The maximum adsorptive desulfurization capacities (Q ) and the molar
0
a
ratios of DBT to metal ion are also presented.
Pseudo-second-order rate
-3
ꢀ1
ꢀ1
Maximum adsorption
constants (k
2
,10 g min mg )
capacity Q
0
DBT/metal
(mol/mol)
ꢁ
ꢀ1
Adsorbent
T ( C) 250 ppmw 500 ppmw
S
S
1000 ppmw
S
(mg S g MOF)
HPW@HKUST-1/c-Al
2
O
3
10
20
2.46 (2.44)
2.51 (2.50)
2.74 (2.63)
2.51 (2.48)
2.65 (2.59)
2.84 (2.66)
2.68 (2.51)
2.73 (2.68)
2.90 (2.78)
70.12 (62.13)
76.34 (70.47)
84.64 (76.10)
0.47 (0.42)
0.52 (0.48)
0.58 (0.52)
(
2 3
HKUST-1/c-Al O )
3
0
a
The values for HKUST-1 are in brackets.
In view of practical applications, investigation of the adsorptive kinetics and ther-
modynamics are necessary to understand enhanced desulfurization performance of
the composite HPW@HKUST-1/c-Al O . The changes of adsorbed amount over the
2
3
composite versus time match well with the pseudo-second-order kinetic model
Supporting Information), meanwhile, the adsorption rate constants (k , Table 3) for
(
2
DBT adsorption are calculated and the constant order is HKUST-1/c-Al O3
˂
2
HPW@HKUST-1/c-Al O . The greater DBT adsorption can be attributed to
2
3
HPW@HKUST-1/c-Al O with shorter diffusion channels and lower diffusion resistance.
2
3
The adsorption isotherms of DBT (Figure S5, supplementary material) show that the
maximum adsorptive desulfurization capacity Q of the composite is higher than that
0
of HKUST-1/c-Al O3 because of acid-base interactions. The molar ratios of the
2
adsorbed DBT to metal site are 0.58 for the composite and 0.52 for HKUST-1/c-Al O
2
3
ꢁ
at 30 C, respectively. Table S4 (supplementary material) shows the Gibbs free energy
DG), enthalpy (DH), and entropy (DS) change. The DG is negative, implying feasible
and spontaneous adsorption. The calculated DH (Figure S6, supplementary material) of
(
ꢀ
1
the DBT adsorption for HKUST-1/c-Al O and the composite is 4.08 and 5.73 kJ mol
,
2
3
respectively, indicating an endothermic adsorption. Because the adsorption process is
a combination of two processes, desorption of the pre-adsorbed solvent molecules
and adsorption of the adsorbate species, the DBT molecules have to displace more
than one n-octane molecule for their adsorption. This results in endothermic adsorp-
tion owing to a stronger interaction between n-octane and the composite than the
interaction between DBT and the composite [52, 62]. The positive DS indicated the
increased randomness during the adsorptive process due to the number of desorbed
solvent molecules being larger than that of the adsorbed adsorbate species [52, 62].
Adsorptive desulfurization experiments and corresponding kinetic and thermo-
dynamic studies for 3-MT, BT, and 4,6-DMDBT were carried out (Supporting
Information) and the adsorptive desulfurization performances are in the same order:
HKUST-1/c-Al O ˂ HPW@KUST-1@c-Al O , implying the composite can be widely used
2
3
2 3
to adsorb different kinds of S-containing compounds (Table 4).
3.3. Study on hydrolysis of ethyl acetate
The Keggin type HPW with strongest Brønsted acidity shows promising applications as
solid-acid catalysts in industry, thus, the hydrolysis of ethyl acetate is chosen as a
probe reaction to assess the acid activity with rates based on catalyst weight and acid
amount of the composite. Table 5 lists the comparison of catalytic activities of the

1
4
L. QIN ET AL.
a
Table 4. The thermodynamic parameters of adsorption of HKUST-1/c-Al O and the composite .
2
3
ꢀ1
ꢁ
ꢀ1
ꢀ1 ꢀ1
Adsorbent
T ( C)
DG (kJmol
)
DH (kJmol
)
DS (Jmol
K )
HPW@HKUST-1/c-Al
2
O
3
10
20
ꢀ11.56 (ꢀ11.36)
ꢀ12.14 (ꢀ12.01)
ꢀ12.74 (ꢀ12.41)
5.73 (4.08)
60.96 (54.40)
(
2 3
HKUST-1/c-Al O )
3
0
a
The values for HKUST-1 are in brackets.
Table 5. Activity of catalysts for ethyl acetate hydrolysis in water.
Acid amount
k
1
k
2
ꢀ
1
ꢀ1
ꢀ1
ꢀ1
ꢀ1
Catalyst
Solid Oxides)
PW/C -AP-SBA [63]
40 [64]
(mmol g
)
(mmol gcat. min
)
(mmol molacid min )
(
8
0.091
0.15
0.0
0.20
0.39
0.31
2.60
25.1
30.1
0.0
25.5
27.6
4.0
275.0
200.6
0.0
127.5
70.8
12.9
0.0
Cs2.5
H0.5PW12O
Cs
SO
3
PW12
O
2
40 [64]
[64]
2
-
4
/ZrO
H-ZSM-5 [64]
Nb [64]
HY zeolite [64]
Organic Resins)
2 5
O
0.0
(
Nafion-H resin [64]
0.80
4.70
161.9
193.6
202.3
41.2
Amberlyst ꢀ1564
(
Liquid Acids)
H
H
3
PW12
O
40 [64]
1.0
19.8
70.4
911.9
70.3
46.1
2
SO
4
[64]
(
MOF)
NENU-3 [26]
NENU-3a [26]
HKUST-1
0.18
0.57
0.0
49.3
178.9
0.0
273.9
313.8
0.0
HKUST-1/c-Al
2
O
3
6.16
0.0
0.0
HPW@HKUST-1/c-Al
2
O
3
0.0979
31.7
325.6
composite and other acid catalysts. The 3.4% conversion of ethyl acetate was obtained
after 2 h reaction using catalyst dosage of 0.2 g. Catalytic activity per acid amount k was
2
ꢀ
1
ꢀ1
calculated as 325.6 mmol molacid min for HPW@HKUST-1/c-Al O . As shown in Table
2
3
5
, the activity per acid amount of HPW@HKUST-1/c-Al O is the highest among all of the
2 3
inorganic and organic solid acids and even exceeds the best former result of 313.8 mmol
ꢀ
1
ꢀ1
molacid min for NENU-3a. The reason to this excellent performance is the formation of
nano-sized HPW@HKUST-1 possessing shorter diffusion channels, larger specific surface
area, and more exposed active sites on the external and internal surface of c-Al O due
2
3
to confinement effect of c-Al O pores and channels. Only ethanol and acetic acid are
2
3
produced during that reaction, indicating no sub-reactions occur. In addition, the reaction
cannot occur in the presence of only HKUST-1, or only HKUST-1/c-Al O , or in absence of
2
3
catalysts, so it can be concluded that a reaction can be assigned to the homogenous
catalysis caused by HPW. In summary, HPW@HKUST-1/c-Al O shows high catalytic activ-
2
3
ity, and there was no deactivation of acid sites by water.
3.4. Study on synthesis of ethyl acetate and n-butyl acetate
Esters are an important class of organic compounds used as plasticizers, perfumes,
artificial spices, etc. [65], and also as essential raw materials for production of fine
chemicals and pharmaceuticals [66]. Especially, ethyl acetate and n-butyl acetate are
important chemicals, environment-friendly organic solvents and diluents, widely

JOURNAL OF COORDINATION CHEMISTRY
15
Figure 7. Effect of reaction time on the esterification for ethyl acetate (a) and n-butyl acetate (b)
over the composite. Reaction conditions: (a) acidmol: alcoholmol, 2:1; catalyst, 0.25 g; temperature,
ꢁ ꢁ
5 C; (b) acidmol:alcoholmol, 2:1; catalyst, 0.4 g; temperature, 110 C.
7
Figure 8. Effect of catalyst amount on the esterification for ethyl acetate (a) and n-butyl acetate
(
7
b) over the composite. Reaction conditions: (a) acidmol: alcoholmol, 2:1; time, 2.5 h; temperature,
ꢁ ꢁ
5 C; (b) acidmol: alcoholmol, 2:1; reaction time, 8 h; temperature, 110 C.
applied in synthesis of dyestuffs, drugs and perfumes. Demand for ethyl acetate and
n-butyl acetate has increased. Thus, synthesis of ethyl acetate and n-butyl acetate is
chosen to assess the acid activity and selectivity of HPW@HKUST-1/c-Al O .
2
3
The effect of the reaction time (Figure 7) and catalyst dosage (Figure 8) on the
esterification is tested under the same conditions. As shown in Figures 7 and 8, ester
conversions increased gradually with the increase in reaction time and catalyst dosage.
The 92.3% and 82.7% conversions were obtained at 2.5 h and 8 h using catalyst dos-
age of 0.25 g and 0.4 g for ethyl acetate and n-butyl acetate, respectively. When the
time was extended to 3.5 h and 10 h, the ester conversions increased only by 0.3%
and 0.2% for ethyl acetate and n-butyl acetate, correspondingly. The ester conversions
are increased only by 0.1% for both ethyl acetate and n-butyl acetate, when the cata-
lyst dosage was increased further to 0.35 and 0.5 g, respectively. Thus, 2.5 h, 0.25 g for
the esterification for ethyl acetate and 8 h, 0.4 g for the esterification for n-butyl acet-
ate are optimal for catalysis. The specific activity per acid amount is 75.4 and

1
6
L. QIN ET AL.
Table 6. Activity of catalysts for synthesis of ethyl acetate and n-butyl acetate.
acidmol
alcoholmol
:
Temperature
Reaction
time (h)
Ester
conversion (%)
ꢁ
Catalyst
Esters
( C)
HPW/K10 [67]
Ethyl acetate
2:1
1:4
1:4
1:4
1:4
1:4
1:4
2:1
1:2
1:2
1:2
1:2
1:2
2:1
100
60
60
60
60
60
60
75
125
125
125
125
80
8
8
89.8
15.5
36
45
29
73
68
92.3
75.5
79.0
53.5
42.7
81
MeIm-PMo [68]
MeIm-PW [68]
MeIm-SiMo [68]
BuIm-PMo [68]
BuIm-PW [68]
BuIm-SiMo [68]
HPW@HKUST-1/c-Al
Al-MCM-41 [69]
20
20
20
20
20
2.5
6
6
6
6
4
2
O
3
3
n-Butyl acetate
H
3
PW12
O
40 [69]
HY [69]
HZSM-15 [69]
SiW12 40/ZrO
HPW@HKUST-1/c-Al
H
4
O
2
[70]
2
O
110
8
82.7
Figure 9. Recyclability of HKUST-1, HKUST-1/c-Al O and the composite for adsorptive desulfuriza-
2
3
tion of DBT at optimum reaction conditions.
ꢀ
1
ꢀ1
1
3.2 mmol molacid min for ethyl acetate and n-butyl acetate, respectively. Notably,
there is no sub-reaction in this esterification and the selectivity is 100%. Table 6 lists
the catalytic activities with ester conversions of HPW@HKUST-1/c-Al O and other acid
2
3
catalysts for comparison. As shown in Table 6, the conversion of ethyl acetate and n-
butyl acetate is 92.3% and 82.7% catalyzed by the composite, respectively, and the
results are superior to other solid acids under optimal conditions.
3
.5. Regeneration performance of the composite HPW@HKUST-1/c-Al O
2 3
There is no doubt that regeneration and stability of the composite as adsorbent and
catalyst are exceedingly important factors in term of industrial applications. The recyc-
lability of the regenerated HPW@HKUST-1/c-Al O as adsorbent is tested in the S-
2
3

JOURNAL OF COORDINATION CHEMISTRY
17
Figure 10. Recyclability of the composite on hydrolysis of ethyl acetate (a), synthesis of ethyl acetate
b) and n-butyl acetate (c). Reaction conditions: (a) 40 mL 5 wt% ethyl acetate; catalyst, 0.2 g; reaction
(
ꢁ
time, 120 min; temperature, 65 C, (b) acidmol: alcoholmol, 2:1; catalyst, 0.25 g; reaction time, 2.5 h; tem-
perature, 75 C; (c) acidmol: alcoholmol, 2:1; catalyst, 0.4 g; reaction time, 8 h; temperature, 110 C.
ꢁ
ꢁ

1
8
L. QIN ET AL.
containing model oil at the same optimum conditions. As shown in Figure 9 for DBT
model oil and Figure S7 (supplementary material) for 3-MT, BT, and 4,6-DMDBT model
oils, the reusable efficiency of HPW@HKUST-1/c-Al O decreased very slightly after the
2
3
6
th cycle, obviously better than HKUST-1 and HKUST-1/c-Al O . The insignificant loss
2 3
of the adsorptive desulfurization performance may be assigned to the chemisorption
caused by Lewis acid-base interactions of direct sulfur-metal bonds. The regenerated
HPW@HKUST-1/c-Al O is also recyclable as acid catalyst under the same reaction con-
2
3
ditions up to six cycles without any change in reactivity and selectivity (Figure 10).
Moreover, no HPW leaching was observed in the product solution under subsequent
recycling by UV–vis spectrum. The IR spectra (Figure S8, supplementary material) and
XRD spectra (Figure S9, supplementary material) of the fresh and sixth regenerated
HPW@HKUST-1/c-Al O after both adsorptive desulfurization and acidic catalysis are
2
3
almost the same so that it can be concluded that the composite possesses high stabil-
ity and immobility. The regeneration efficiency is due to the formation of secondary
bonding, such as hydrogen bonding between hydroxyl groups of c-Al O and carbox-
2
3
-
ylic groups of BTC3 or Van der Waals interactions [36, 37], which prevent aggregation
and deletion of nano-sized HPW@HKUST-1. In addition, the HKUST-1/c-Al O compo-
2
3
sites can be easily recovered by simple decantation due to its millimeter size and
enhanced mechanical strength.
4. Conclusion
We prepared a hierarchical multiporous composite HPW@HKUST-1/c-Al O in which
2
3
HPW is included in the host matrix of HKUST-1 loaded on the c-Al O beads through
2
3
one-step hydrothermal reaction. The composite HPW@HKUST-1/c-Al O3 not only
2
shows excellent adsorptive desulfurization performance owing to the beneficial acid-
base interaction between acidic HPW and slightly basic sulfur-containing compounds,
but also shows high acidic activity in hydrolysis of ethyl acetate and synthesis of ethyl
acetate and n-butyl acetate owing to the high dispersion and easy access of HPW in
the composite. The composite material can be easily regenerated by acetone washing
and reused for many times with small decrease in adsorptive desulfurization capacity
and acid catalytic activity, suggesting potential as adsorbent and acid catalyst in prac-
tical applications.
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
The authors acknowledge the Natural Science Foundation of China, the Fundamental Research
Funds for the Central Universities under Grant no. XK1802-6. Dr Libo Qin acknowledges
Educational Commission of ShanXi Province of China under Grant no. 2019L0910. Prof. Xue
Duan of Beijing University of Chemical Technology is also acknowledged for his kind support.

JOURNAL OF COORDINATION CHEMISTRY
19
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