Zirconium-Gallic Acid Coordination Polymer: Catalytic Transfer Hydrogenation of Levulinic Acid and Its Esters into γ-Valerolactone

Article abstract of DOI:10.1007/s10562-021-03724-3

The conversion of ethyl levulinate (EL) to produce γ-valerolactone (GVL) through catalytic transfer hydrogenation (CTH) reaction plays a crucial role in the field of biomass catalytic conversion. In this work, a novel Zr-base catalyst with phenate group, phenolic hydroxyl and carboxyl in its structure was prepared by the co-precipitation of natural sources gallic acid and ZrCl₄. It was found that Zr-GA has an excellent catalytic performance for this reaction and satisfactory GVL yield could be achieved. Besides, Zr-GA could be easily separated from the reaction system and reused at least six times without a significantly decrease in activity. Meanwhile, various characterizations had proved that Zr-GA is a porous material with acid–base bifunctional sites. The main reason for the high catalytic activity of the Zr-GA was that the synergetic effects of Lewis acid/base sites and Br?nsted acid sites and appropriate textural properties. In addition, a possible reaction mechanism was proposed in conjunction with the poisoning experiment and previous reports. The heterogeneous catalyst Zr-GA prepared with gallic acid as a raw material has low cost and recyclability, and has great potential in green chemistry. Graphical Abstract: [Figure not available: see fulltext.]

Full text of DOI:10.1007/s10562-021-03724-3

Catalysis Letters
https://doi.org/10.1007/s10562-021-03724-3
Zirconium‑Gallic Acid Coordination Polymer: Catalytic Transfer
Hydrogenation of Levulinic Acid and Its Esters into γ‑Valerolactone
Xiaoning Li1 · Yehui Li1 · Xiang Wang1 · Haijun Wang1
Received: 4 May 2021 / Accepted: 28 June 2021
© The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2021
Abstract
The conversion of ethyl levulinate (EL) to produce γ-valerolactone (GVL) through catalytic transfer hydrogenation (CTH)
reaction plays a crucial role in the feld of biomass catalytic conversion. In this work, a novel Zr-base catalyst with phenate
group, phenolic hydroxyl and carboxyl in its structure was prepared by the co-precipitation of natural sources gallic acid and
ZrCl4. It was found that Zr-GA has an excellent catalytic performance for this reaction and satisfactory GVL yield could be
achieved. Besides, Zr-GA could be easily separated from the reaction system and reused at least six times without a signif-
cantly decrease in activity. Meanwhile, various characterizations had proved that Zr-GA is a porous material with acid–base
bifunctional sites. The main reason for the high catalytic activity of the Zr-GA was that the synergetic efects of Lewis acid/
base sites and Brønsted acid sites and appropriate textural properties. In addition, a possible reaction mechanism was pro-
posed in conjunction with the poisoning experiment and previous reports. The heterogeneous catalyst Zr-GA prepared with
gallic acid as a raw material has low cost and recyclability, and has great potential in green chemistry.
Graphical Abstract
Extended author information available on the last page of the article
Vol.:(0123456789)
1 3

X. Li et al.
Keywords Ethyl levulinate · γ-valerolactone · Zr-GA · Catalytic transfer hydrogenation
multifunctional materials formed by chelating with metal
ions [35]. Gallic acid is a kind of polyphenol compound,
which is widely found in tea and it has been widely used
in anti-oxidation and medicine [36]. In this work, we used
gallic acid and ZrCl4 as raw materials to synthesize a series
of Zr-GA-x catalysts with diferent molar ratios in N,N-
dimethylformamide and triethylamine. Using alcohol as a
solvent and H-donor, LA and its esters were converted to
GVL through CTH. It was found that the prepared Zr-GA-x
can catalyze the CTH reaction to provide a satisfactory yield
of GVL. As far as we know, this is the frst report about the
organic–inorganic hybrid catalyst Zr-GA-x has been used in
the CTH reaction of LA and its esters to produce GVL, and
the catalyst has the advantages of wide source of raw materi-
als, easily assemble synthesis and high stability.
1 Introduction
Due to the increasingly serious problems between the
exploitation and use of fossil fuels and the environment,
economy and politics, one of the most serious challenges
of the 21st century is to replace fossil fuels with more sus-
tainable alternatives [1, 2].As the world’s most important
sustainable renewable green resource, biomass accounts for
about 14% of the world total annual energy consumption. It
is the fourth largest energy source after oil, coal, and natural
gas, and becoming a kind of renewable substitutes that can
replace petroleum-based resources are valued and favored by
all countries [3, 4]. So far, various value-added chemicals
have been obtained from biomass, such as 5-hydroxymeth-
ylfurfural, lactic acid, furfural, furfuryl alcohol, levulinic
acid (LA), alkyl levulinate, and γ-valerolactone (GVL), etc.
[5–11]. Among them, GVL has the property of non-toxic
and biodegradable, which can be used as a green solvent
and an intermediate for the production of high value-added
chemicals and high-performance liquid fuels [12–14].
Carbonyl compounds can be reduced to alcohols through
catalytic transfer hydrogenation (CTH) reactions. In this
reaction, the alcohols used as a solvent and hydrogen source,
and fnally dehydrogenated to a ketone. CTH is a typical
Meerwein–Ponndorf–Verley reaction and it is widely used
in the reduction of carbonyl compounds. The use of a large
number of safe secondary alcohols instead of dangerous
gaseous hydrogen as H-donor makes it an ideal reduction
technology for carbonyl compounds [15–17]. The methods
of producing GVL mainly include direct hydrogenation
and transfer hydrogenation. Between them, direct hydro-
genation uses H2 as a hydrogen source, which is not only
costly, but has safety risks. At present, most of the research-
ers have solved the above-mentioned problems by means of
transfer hydrogenation, using LA and its esters to prepare
GVL through CTH. A large number of catalysts have been
reported for this reaction, such as Zr-containing zeolite,
ZrO2, MOFs, GO, zirconium phosphates, supported heter-
opolyacid, metal hydroxides, organic–inorganic hybrid cata-
lysts, etc. [18–26]. Among them, zirconium-based materials
have received extensive attention due to their wide range of
applications, in addition to being used for catalysis, they
can also be used for adsorption and separation [27, 28]. So
far, numerous Zr-containing organic–inorganic hybrid cata-
lysts have been developed for the CTH reaction of LA and
its esters, such as Zr-PhyA, Zr-HBA, Zr-CA, Zr-TMPA, Zr-
TPPA-3, Zr-HPAA, etc. [29–34].
2 Experimental Section
2.1 Chemicals
Methyl levulinate (ML), ethyl levulinate (EL), butyl levuli-
nate (BL), LA, ZrCl4, gallic acid (GA), GVL, N,N-dimeth-
ylformamide (DMF), triethylamine, methanol, ethanol,
n-propanol, isopropanol, 1-butanol, tert-butanol, 3-pentanol,
benzoic acid, 2,6-lutidine, pyridine and naphthalene are of
analytical grade and used without further treatment.
2.2 Catalyst Preparation
The preparation method of the as-prepared catalyst was
referred to the previous literature and was modifed [29]. In
a general procedure, 0.476 g (2 mmol) of ZrCl4 and 0.344 g
(1 mmol) of GA dissolve in DMF (20 mL) with the aid of
ultrasound, respectively. Then, the GA solution was added
dropwise to the ZrCl4 solution. After the mixture was clari-
fed, 3 mL of triethylamine was added dropwise, stirred vig-
orously at room temperature for 2 h and then aged at 80 °C
for 8 h. The mixed solution after aging was fltered, washed
with DMF and ethanol. The obtained solid was placed in a
vacuum drying oven at 80 °C for 14 h and then grounded to
obtain Zr-GA. For comparison, diferent Zr-GA-x catalysts
were synthesized by changing the raw material ratio, using
x mmol of ZrCl4 and 1 mmol of GA (x=1, 2, 3, 4), named
Zr-GA-1, Zr-GA-2/Zr-GA, Zr-GA-3, Zr-GA-4, respectively.
2.3 Catalyst Characterization
The synthesis of multifunctional materials using natu-
ral sources of chemical substances is becoming more and
more important in the feld of synthetic chemistry, especially
Fourier transform infrared (FT-IR) spectra were detected
with a Nicolet 360 FT-IR instrument (KBr pellet) in the
1 3

Zirconium-Gallic Acid Coordination Polymer: Catalytic Transfer Hydrogenation of Levulinic…
range of 4000–600 cm−1. X-ray difraction (XRD) patterns
were recorded on a Bruker D8 Advance difractometer with
Cu Ka radiation and 2θ recorded from 5° to 90° at 30 kV and
10 mA. Scanning electron microscopy (SEM) images were
obtained using a HITACHI S-4800 scanning electron micro-
scope at 3 kV. Transmission electron microscopy (TEM)
measurement was performed on a JEOL JEM-2100 micro-
scope at 200 kV. The N2 adsorption–desorption isotherm
(BET) was measured using a Micromeritics ASAP 2020
instrument, samples were degassed at 120 °C for 12 h in
a vacuum before N2 absorption. Temperature-programmed
desorption of ammonia/carbon dioxide (NH3/CO2-TPD)
was performed on Micromeritics AutoChem II 2920 Chem-
isorption analyzer, the sample (50 mg) was charged into
quartz reactor and preheated at 300 °C for 1 h at a rate of
10 °C min−1 under a fow of He (50 cm3 min−1). Then the
temperature was dropped to 50 °C, NH3/CO2 (50 cm3 min−1)
was pulsed into the reactor in He fow until the acid sites
was saturated. The absorbed NH3 was removed with He and
the temperature was raised from 60 to 600 °C at a rate of
10 °C min−1 after waiting for baseline stabilization. The con-
centration of Zr in the reaction solution were determined by
inductively coupled plasma optical emission spectroscopy
(ICP-OES) which performed on PE Optima 8000.
conversion of EL and yield of GVL were calculated by the
formula following:
Moles of GVL formed
Yield of GVL =
× 100%
(1)
Moles of EL used
Moles of EL converted
Moles ofEL used
Conversion of EL =
× 100%
(2)
2.5 Leaching Test and Reusability Test
To investigate the heterogeneity of the catalyst, it was
removed from the reaction mixture after 7 h and then the
reaction was continued. In the reusability tests, the spent
catalyst was recovered by centrifugation and washed three
times with isopropanol. After drying under vacuum at 80 °C
for 14 h, the catalyst was reused for the next run.
3 Results and Discussion
3.1 Catalyst Characterization
The FT-IR spectra of GA and Zr-GA-x are shown in Fig. 1a.
The strong peak at about 3400 cm−1 was the stretching vibra-
tion of the sample physically adsorbing water and hydroxyl
groups [19]. The peak at 1670 cm−1 was attributed to the
stretching vibration of the –COOH group, indicating that
–COOH was present in both of GA and Zr-GA-x, demon-
strating Zr was not coordinated with –COOH. At the same
time, the FT-IR spectra of Zr-GA-x and GA all showed the
characteristic asymmetric and symmetric stretching vibra-
tion of the phenolic hydroxyl group, and the correspond-
2.4 CTH of EL to GVL
The CTH reaction from EL to GVL was carried out in a
25 mL Tefon-lined stainless-steel reactor equipped with a
magnetic stirrer. In a typical procedure, EL (1 mmol), iso-
propanol (5 mL), and the catalyst (0.2 g) were added into
the reactor. The reactor was sealed and placed into a pre-
heated oil-bath at a desired temperature for a known time.
At the end of the reaction, the reactor was cooled to room
temperature and the liquid samples were collected and ana-
lyzed by gas chromatography (GC 9790) using naphthalene
as the internal standard, and identifcation of the liquid
products was identifed by GC–MS (ULTRA QP2010). The
ing ranges were 1613–1580 cm−1 and 1499–1467 cm−1
,
respectively. Compared with GA, the wavenumber difer-
ence of Zr-GA-x was reduced from 155 to 85 cm−1, 87 cm−1,
87 cm−1 and 84 cm−1, respectively, which proved that Zr and
Fig. 1 Characterization of
Zr-GA-x. a FT-IR spectra, b
Powder XRD pattern
1 3

X. Li et al.
the phenolic hydroxyl group in GA were successful coor-
dinated [37]. According to the previously reported related
literature, it was inferred that only two adjacent phenolic
hydroxyl groups in GA coordinate with Zr [38–41]. In addi-
tion, the peak appearing at 477 cm−1 was attributed to the
Zr–O bond.
The crystal form of Zr-GA-x was explored by X-ray dif-
fractometer. It can be seen from the Fig. 1b that Zr-GA-x
had broad difraction peaks, indicating that Zr-GA-x was
an amorphous material with low crystallinity, and the low
crystallinity might be due to the weak coordinating group
(phenolic hydroxyl) in the structure [42]. The surface mor-
phology and internal composition of Zr-GA-x catalyst were
observed by SEM and TEM, the images are shown in Fig. 2.
It can be seen that Zr-GA-x had no uniform shape, and the
gap between the aggregated particles leaded to the porosity
of the catalyst, which is consistent with the XRD result [32].
Meantime, the pore structure of the Zr-GA-x catalyst was
checked by N2 adsorption–desorption, and the results are
shown in Fig. 3 and Table 1. It can be seen that the iso-
therms of Zr-GA-x exhibited type IV mode, showing obvi-
ous hysteresis loops, indicating that there was an irregular
mesoporous structure in the Zr-GA-x catalyst. Consistent
with the SEM and XRD results, the pores of the catalyst
originated from the gaps between the aggregated particles. It
can be seen from Table 1 that Zr-GA has the largest specifc
surface area, which is conducive to the abundant contact of
the substrate with the active sites of Zr-GA, hence improving
the catalytic activity.
Fig. 2 SEM of Zr-GA-1 (a), Zr-GA (b), Zr-GA-3 (c), Zr-GA-4 (d)
and TEM of Zr-GA (e)
Fig. 3 N2 adsorption–desorp-
tion isotherm of Zr-GA-x. a
Zr-GA-1, b Zr-GA, c Zr-GA-3
and d Zr-GA-4
1 3

Zirconium-Gallic Acid Coordination Polymer: Catalytic Transfer Hydrogenation of Levulinic…
Table 1 Textural properties of Zr-GA-x
of Zr and GA was essential for the CTH reaction for the
conversion of EL to GVL. Therefore, Zr-GA was used as
a catalyst to study the infuence of other parameters on the
reaction. Besides, the results of reaction conditions and
activities of the Zr-GA catalyst and other reported catalytic
systems have been summarized in Table S1.
Entry
Catalysta
Surface area
(m2/g)b
Pore diameter
(nm)c
Pore
volume
(cm3/g)d
1
2
3
4
Zr-GA
142.1
117.2
133.14
30.03
9.39
0.35
Zr-GA-1
Zr-GA-3
Zr-GA-4
4.224
6.427
4.015
0.395
0.433
0.058
3.3 Efect of Reaction Temperature and Time
aThe samples were degassed at 120 °C for 12 h
bSurface area based on multipoint BET method
cPore volume based on BJH method
During the reaction process, the trend of EL conversion
and GVL yield with the reaction temperature and time is
shown in Fig. 4. When the temperature increased from 140
to 160 °C, both the conversion of EL and the yield of GVL
showed a rapid upward trend. The yield of GVL reached
the maximum at 160 °C, indicating that high temperature
promoted the reaction. However, when the temperature
further increased to 170 °C, the yield of GVL began to
decrease (Table 2, entry 8), which may be that higher tem-
perature would cause the presence of side reactions and
other by-products. Through the previous reports and the
analysis of the substrate, we can infer that the by-product
was isopropyl levulinate produced by the transesterifca-
tion of EL and isopropanol [25, 32]. The efect of reaction
time on the CTH reaction of EL was studied in the range of
5–10 h. It can be seen from Fig. 4 that when the reaction
temperature is 140–150 °C, both the EL conversion and
the GVL yield continue to increase with the extension of
the reaction time. As the temperature continued to rise to
160 °C, the EL conversion and GVL yield increased stead-
ily and reached the maximum at 8 h, 98.58% EL conver-
sion and 94.23% GVL yield were obtained, respectively.
When the reaction time was further extended to 10 h, both
the EL conversion and GVL yield decreased, which may
be due to the beginning of GVL converted into other by-
products. Therefore, the optimal reaction temperature was
160 °C, and the optimal reaction time was 8 h.
dPore diameter based on BJH method
3.2 Catalyst Screening
In the CTH reaction of converting EL to GVL, it is of great
importance to select an excellent catalyst. Therefore, we
explored the efects of diferent types of catalysts on the
reaction in the initial investigation. As shown in Table 2,
without the addition of catalyst, no reaction occurred
(entry1). When using Zr-GA-x as the catalyst (entries 2–5),
it can be seen that Zr-GA has the highest catalytic activ-
ity, the EL conversion and the GVL yield were reached
98.58% and 94.23%, respectively. Other Zr-GA-x also
reached satisfactory EL conversion, meantime, the GVL
yield was ranked as Zr-GA>Zr-GA-4>Zr-GA-1>Zr-GA-
3, which can be seen that the catalytic efect had a wireless
relationship with the magnitude of x. When ZrO2 was used
as a catalyst, a medium yield of GVL was obtained (entry
7), indicating that Zr was the active site of the reaction.
Conversely, when GA was used as a catalyst and added to
the reaction system (entry 6), there was almost no catalytic
activity. These above results all indicated that the Lewis
acid–base sites (Zr4+–O2−) obtained by the coordination
Table 2 Comparison of
Entry
Catalyst
Temperature
( °C)
Time (h)
CEL (%)
YGVL (%)
SGVL (%)
diferent catalysts for the CTH
reaction of EL to produce GVLa
1
2
3
4
5
6
7
8
None
160
160
160
160
160
160
160
170
8
8
8
8
8
8
8
8
0
0
0
Zr-GA
Zr-GA-1
Zr-GA-3
Zr-GA-4
GA
ZrO2
Zr-GA
98.58
96.24
97.61
98.88
10.42
36.46
99.46
94.23
63.56
60.01
78.44
1.16
30.42
87.56
95.59
66.04
61.48
79.33
11.13
83.43
88.04
CEL conversion of EL; YGVL yield of GVL; SGVL selectivity of GVL
aReaction condition: EL (0.144 g, 1 mmol), catalyst 0.2 g, iso-propanol 5 mL
1 3

X. Li et al.
Fig. 4 Efect of reaction time
and temperature on the EL
conversion (a) and GVL yield
(b). Reaction conditions: EL
(0.144 g, 1 mmol), catalyst
0.2 g, isopropanol 5 mL
Table 3 The efect of the diferent H-donor on the CTH reaction of
EL to GVL
Entry
Solvents
CEL(%)b
YGVL(%)b
1
2
3
4
5
6
7
Methanol
Ethanol
n-propanol
2-butanol
tert-butanol
3-pentanol
Isopropanol
77.42
74.21
74.19
85.35
13.21
68.45
98.58
9.4
19.24
24.32
73.65
0
83.56
94.23
CEL conversion of EL; YGVL yield of GVL
aReaction conditions:0.20 g Zr-GA; 5 mL H-donor; 1 mmol EL; reac-
tion temperature:160 °C; reaction time:8 h
bProduct analysis were determined by GC
Fig. 5 Efect of catalyst amount. Reaction conditions: EL (0.144 g,
1 mmol), isopropanol 5 mL, reaction temperature 160 °C, reaction
time 8 h
3.5 Catalytic Efect of H‑Donor
The H-donor is a crucial parameter in the CTH reaction
which acts as both a H-donor and a solvent. Therefore,
primary alcohols (methanol, ethanol, n-propanol), second-
ary alcohols (isopropanol, 2-butanol, 3-pentanol) and tert-
butanol were used as H-donor to study their efects on the
CTH reaction of EL, and the results are shown in Table 3.
When using primary alcohols as H-donor, high EL conver-
sion could be obtained, however, the yield of GVL were
relatively low (entries 1–3). When tert-butanol was used as
a H-donor, the EL conversion was extremely low, indicat-
ing the presence of α-H in the alcohol was essential for the
CTH reaction (entries 5) [44]. Therefore, primary and ter-
tiary alcohols were not suitable as H-donor for CTH reac-
tions. On the contrary, when using the secondary alcohols
as H-donor, satisfactory EL conversion and GVL yield could
be obtained (entries 4 and 6–7). With the extension of the
carbon chain in the secondary alcohol, the conversion of EL
decreased slightly. The possible reason for this phenomenon
was that the extension of the secondary alcohol carbon chain
would cause greater negative steric hindrance, preventing
3.4 Efect of the Dosage of Catalyst
After exploring the efect of reaction temperature and time
on the CTH reaction of EL, the dosage of catalyst added
to the reaction system was studied under the reaction con-
ditions of 160 °C and 8 h. As shown in Fig. 5, when the
dosage of Zr-GA was 75–200 mg, as the dosage increased,
both the EL conversion and the GVL yield increased rap-
idly, which may be due to the presence of more available
active sites in the reaction system, which promoted the
progress of the reaction. Subsequently, the dosage of cata-
lyst continued to increase to 300 mg, the EL conversion
and GVL yield began to decrease, which may be due to the
excessive amount of catalyst would lead to poor dispers-
ibility of the Zr-GA particles and have a negative impact
on the mass transfer of the reaction [43]. Therefore, the
addition of 0.2 g of Zr-GA would be the best choice for
this reaction.
1 3

Zirconium-Gallic Acid Coordination Polymer: Catalytic Transfer Hydrogenation of Levulinic…
the difusion of substrate molecules into the pores of Zr-GA
[37]. Therefore, in the CTH reaction of converting EL to
GVL, isopropanol would be the best choice of the H-donor
and solvent.
3.7 The Leaching Test and Reusability
of the Catalyst
The heterogeneous catalyst has the advantages of easy recy-
cling, cost reduction, and extremely good potential applica-
tion value in the reaction of converting biomass into high
value-added chemicals. Firstly, the heterogeneity of Zr-GA
was checked by leaching test. It can be seen from Fig. 6a
that the yield of GVL was around 85.23% after removing
the Zr-GA, indicating that no active sites were leached into
the reaction solution and Zr-GA had excellent heterogene-
ity. On the contrary, as the Zr-GA remained in the reaction
system, the GVL yield increased continuously and eventu-
ally decreased. Secondly, the reusability of the catalyst was
explored, and the results have shown in Fig. 6b. It was found
that Zr-GA still had great catalytic activity after six cycles,
and the yield of GVL was only slightly lower than that of
the frst cycle. The reaction solution after the sixth cycle was
checked by ICP-OES, and it was found that the concentration
of Zr was lower than 1.7 ppm. The decrease in catalyst activ-
ity may be due to the leaching of a small amount of Zr active
sites. In addition, the Zr-GA after six cycles was character-
ized by FT-IR, XRD, SEM, and TEM. It can be seen from
Fig. 7 that the amorphous morphology and microstructure
of Zr-GA did not change much. In addition, the new peak
around 2900 cm−1 appeared in recovered Zr-GA in Fig. 7a
might be due to the deposition of humins on the surface of
Zr-GA. In summary, Zr-GA had outstanding heterogeneity
and could be reused several times.
3.6 Catalytic Efect of Zr‑GA on Diferent Substrates
It can be seen from previous studies that Zr-GA has high
catalytic activity for the CTH reaction of converting EL
to GVL. Therefore, the catalytic performance of Zr-GA in
the reaction of preparing GVL from other substrates was
examined under optimal conditions. As shown in Table 4,
when ML was used as a substrate, Zr-GA had high catalytic
activity for the reaction, 98.32% ML conversion and 96.63%
GVL yield were obtained (entry 2). On the contrary, BL
showed lower reactivity than ML and EL, which may be due
to the larger steric hindrance of butyl, only 81.56% of GVL
yield was obtained (entry 4). In addition, LA could be easily
converted to GVL. When the reaction time was 4 h, 100%
LA conversion and 96.63% GVL yield could be achieved
(entry 1). This phenomenon may be caused by the acidity
of LA itself, which made the key intermediate 4-hydroxy-
valeric acid lactonization faster, therefore generating GVL
in a shorter time [25].
Table 4 The conversion of LA and its eaters into GVL through CTH
reaction catalyzed by Zr-GAa
Entry
Substrate
Time (h)
CEL (%)b
YGVL (%)b
3.8 Explanation of the High Activity of Zr‑GA
1
2
3
4
LA
ML
EL
BL
4
8
8
8
100
96.63
93.38
94.23
81.56
98.32
98.58
91.48
According to previous reports, the infuence of the acid-
ity and basicity of the catalyst on the CTH reaction of EL
cannot be ignored. First, we checked the acidity of Zr-GA
by NH3-TPD. It can be seen from Fig. 8a that Zr-GA has
two desorption peaks at 160 °C and 377 °C, corresponding
to the weak acid site and the medium strong acid site, and
the acidity was 1.55 and 2.70 mmol g−1, respectively. The
CEL conversion of EL; YGVL yield of GVL
aReaction conditions: substrate (1 mmol), isopropanol (5 mL), Zr-GA
(0.20 g), temperature (160 °C)
bProduct analysis were determined by GC
Fig. 6 Leaching test of Zr-GA
for the CTH of EL to produce
GVL (a) and recycle experiment
of the Zr-GA (b). Reaction con-
ditions: EL (0.144 g, 1 mmol),
catalyst 0.2 g, isopropanol
5 mL, reaction temperature
160 °C, reaction time 8 h
1 3

X. Li et al.
Fig. 7 The characterization of
the Zr-GA after reused for six
times. a FT-IR spectrum, b
XRD pattern, c SEM image and
d TEM image
Fig. 8 NH3-TPD (a) and
CO2-TPD (b) of Zr-GA
frst peak at 160 °C corresponded to a weak acid site, which
was derived from Zr4+ and the phenolic hydroxyl group that
were not coordinated with Zr in the GA structure. Gener-
ally speaking, the metal in the metal–ligand coordination
polymer is Lewis acidic [45]. The second desorption peak
was related to the -COOH group which was not coordinated
with Zr in the GA structure. The existence of a large num-
ber of acidic sites can activate the activation of C=O in the
substrate, therefore improving the reactivity [29].
large number of phenate groups present in Zr-GA. Accord-
ing to reports, the phenate group can increase the basic-
ity of the catalyst [30]. Higher basicity was conducive to
the dissociation of the hydroxyl group in the isopropanol
molecule, consequently increasing the CTH reactivity of
EL [29, 46].
Except for the acidity and basicity of the catalysts, the
textural properties of the catalyst might also afect the
catalytic activity. As shown in Table 1, compared with
other Zr-GA-x, Zr-GA has the largest specifc surface area,
which promotes the difusion of the substrate to the active
center of Zr-GA, hence achieving a better catalytic efect
[31].
Secondly, the basicity of Zr-GA was checked by
CO2-TPD. It can be seen from Fig. 8b that there are a large
number of basic sites in the Zr-GA catalyst, and the total
amount is 4.98 mmol g−1, which was originated from the
1 3

Zirconium-Gallic Acid Coordination Polymer: Catalytic Transfer Hydrogenation of Levulinic…
the acid–base sites in the Zr-GA catalyst were signifcant for
3.9 Poisoning Experiment
the high catalytic performance.
From the previous discussion, it is clear that the acid–base
site is critical in the reaction of EL through CTH to pre-
pare GVL. At the same time, the results of NH3-TPD and
CO2-TPD also indicate that Zr-GA contains a large number
of acid–base sites. Meantime, the acidic sites were mainly
derived from Zr4+, the –COOH and phenolic hydroxyl
groups originated from GA, and the basic sites were mainly
derived from O2− in the phenate groups. In order to explore
the efect of acid–base sites on the reaction, benzoic acid,
2,6-lutidine and pyridine were used to poison Lewis basic
sites, Brønsted acid sites and Lewis acid sites, respectively.
As shown in Table 5, when benzoic acid was added to the
reaction system, it was observed that the GVL yield and EL
conversion decreased signifcantly. This may be due to the
strong interaction between the benzoic acid and the basic
sites of Zr-GA, indicating that the CTH reaction catalyzed
by Zr-GA was closely related to basic sites. The addition of
pyridine also reduced the GVL yield and EL conversion.
When 2,6-lutidine was used to poison Brønsted acidic sites,
the EL conversion and GVL yield only slightly decreased,
indicating that Brønsted acid sites can promote the CTH
reaction. According to previous literature reports, compared
with benzoic acid, 2,6-lutidine and pyridine have weaker
poisoning efects [47]. Consequently, due to the partial
poisoning of acid sites, the addition of 2,6-lutidine and
3.10 Plausible Mechanism
It can be seen from the previous discussion that acidic and
basic sites are indispensable for the CTH reaction. Based
on previous reports and the above analysis, we proposed
a possible reaction mechanism for Zr-GA to catalyze the
conversion of LA and its esters to GVL (Scheme 1) [38, 39,
41]. First, isopropanol interacts with the acid–base coupled
sites (–Ar–O2–Zr–) on Zr-GA and dissociates into alkoxide
and hydrogen protons. At the same time, the electron-with-
drawing Brønsted acid site (Ar–OH) activates the C=O in
the structure of LA and its ester, and then the activated C=O
and the dissociated isopropanol form a six-membered ring
transition state and undergo hydrogen transfer to produce
4-hydroxyvaleric acid and its esters. Finally, under the action
of the acidic sites of Zr-GA, 4-hydroxyvaleric acid and its
esters undergo intramolecular esterifcation or transesterif-
cation to produce the fnal product GVL.
4 Conclusions
In summary, we synthesized a new Zr-based heterogeneous
catalyst (Zr-GA) with natural resource gallic acid as ligand
through a simple co-precipitation method, and applied it to
the reaction of LA and its esters to prepare GVL through
CTH reaction. Characterization and experimental results
showed that Zr-GA has excellent catalytic activity. Under
the optimized reaction conditions, the LA and its esters con-
version and GVL yield could reach more than 90%. The high
activity of the catalyst is attributed to the synergistic efect
of Lewis acid sites from Zr4+, Brønsted acid sites from phe-
nolic hydroxyl groups, and Lewis base sites from phenolate
groups. In addition, the Zr-GA catalyst can be reused six
times without signifcantly catalytic activity loss. Finally, a
possible reaction mechanism for the conversion of LA and
its esters to produce GVL was proposed. Due to Zr-GA has
the characteristics of low cost and recyclability, it has poten-
tial applications in the catalytic conversion of biomass and
its derivatives.
Table 5 Study on the activity of Zr-GA by benzoic acid, 2,6-lutidine
and pyridinea
Entry
additives
CEL (%)
YGVL (%)
SGVL (%)
1
2
3
4
No
98.58
61.53
90.25
87.32
94.23
43.95
86.34
79.65
95.59
71.43
95.67
91.22
Benzoic acid
2,6-lutidine
Pyridine
CEL conversion of EL; YGVL yield of GVL; SGVL selectivity of GVL
aReaction environments: 0.20 g Zr-GA; 5 mL isopropanol; 1 mmol
EL; reaction temperature:160 °C; reaction time: 8 h
pyridine only slightly reduced the EL conversion and GVL
yield. The above poisoning experiment further proved that
1 3

X. Li et al.
Scheme 1 Plausible mechanism of CTH reaction of EL into GVL over Zr-GA
7. Vorholt AJ, Esteban J (2020) An overview of the biphasic dehy-
dration of sugars to 5-hydroxymethylfurfural and furfural: a
rational selection of solvents using COSMO-RS and selection
guides. Green Chem. https://doi.org/10.1039/c9gc04208c
8. Wang T, Hu A, Xu G et al (2019) Porous Zr–thiophenedicarbo-
xylate hybrid for catalytic transfer hydrogenation of bio-based
furfural to furfuryl alcohol. Catal Lett 149:1845–1855. https://
doi.org/10.1007/s10562-019-02748-0
Supplementary Information The online version contains supplemen-
tary material available at https://doi.org/10.1007/s10562-021-03724-3.
Acknowledgements We thank Postgraduate Research & Practice Inno-
vation Program of Jiangsu Province (No. KYCX20_1777)
Declarations
9. Wang J, Cui H, Wang Y et al (2020) Efcient catalytic conversion
of cellulose to levulinic acid in the biphasic system of molten salt
hydrate and methyl isobutyl ketone. Green Chem 22:4240–4251.
https://doi.org/10.1039/d0gc00897d
Conflict of interest The authors declare no confict of interests.
10. Li X, Li Y, Wang X et al (2021) Zr-DBS with sulfonic group:
a green and highly efcient catalyst for alcoholysis of furfuryl
alcohol to ethyl levulinate. Catal Lett. https://doi.org/10.1007/
s10562-020-03516-1
References
1. O’Neill B (2003) Planning for future energy resources. Science
300:581b–5584. https://doi.org/10.1126/science.300.5619.581b
2. Ragauskas AJ, Williams CK, Davison BH et al (2006) The path
forward for biofuels and biomaterials. Science 311:484–489.
https://doi.org/10.1126/science.1114736
11. Lai J, Zhou S, Liu X et al (2019) Catalytic transfer hydrogenation
of biomass-derived ethyl levulinate into gamma-valerolactone
over graphene oxide-supported zirconia catalysts. Catal Lett
149:2749–2757. https://doi.org/10.1007/s10562-019-02835-2
12. Du XL, Bi QY, Liu YM et al (2012) Tunable copper-catalyzed che-
moselective hydrogenolysis of biomass-derived γ-valerolactone
into 1,4-pentanediol or 2-methyltetrahydrofuran. Green Chem
14:935–939. https://doi.org/10.1039/c2gc16599f
3. Luterbacher JS, Rand JM, Alonso DM et al (2014) Nonenzy-
matic sugar production from biomass using biomass-derived
γ-valerolactone. Science 343:277–280. https://doi.org/10.1126/
science.1246748
13. Bruno TJ, Wolk A, Naydich A (2010) Composition-explicit
distillation curves for mixtures of gasoline and diesel fuel with
γ-valerolactone. Energy Fuels 24:2758–2767. https://doi.org/10.
1021/ef100133a
4. Xue Z, Yu D, Zhao X, Mu T (2019) Upgrading of levulinic acid
into diverse N-containing functional chemicals. Green Chem
21:5449–5468. https://doi.org/10.1039/c9gc02415h
5. Le GTT, Arunaditya K, Panichpol J, Rodruangnon T (2021) Sul-
fonated magnetic carbon nanoparticles from eucalyptus oil as a
green and sustainable catalyst for converting fructose to 5-HMF.
Catal Commun. https://doi.org/10.1016/j.catcom.2020.106229
6. Ponchai P, Adpakpang K, Thongratkaew S et al (2020) Engineer-
ing zirconium-based UiO-66 for efective chemical conversion
of d-xylose to lactic acid in aqueous condition. Chem Commun
56:8019–8022. https://doi.org/10.1039/d0cc03424j
14. Zhao Y, Fu Y, Guo QX (2012) Production of aromatic hydrocar-
bons through catalytic pyrolysis of γ-valerolactone from biomass.
Bioresour Technol 114:740–744. https://doi.org/10.1016/j.biort
ech.2012.03.057
15. Nishide K, Shigeta Y, Obata K, Node M (1996) Asymmet-
ric 1,7-hydride shift: the highly asymmetric reduction of α,
β·unsaturated ketones to secondary alcohols via a novel tandem
1 3

Zirconium-Gallic Acid Coordination Polymer: Catalytic Transfer Hydrogenation of Levulinic…
32. Xie Y, Li F, Wang J et al (2017) Catalytic transfer hydrogenation
Michael addition-Meerwein–Ponndorf–Verley reduction. J Am
Chem Soc 118:13103–13104. https://doi.org/10.1021/ja963098j
16. Evans DA, Nelson SG, Gagné MR, Muci AR (1993) A chiral
samarium-based catalyst for the asymmetric Meerwein-Ponndorf-
Verley reduction. J Am Chem Soc 115:9800–9801. https://doi.org/
10.1021/ja00074a057
of ethyl levulinate to Γ-valerolactone over a novel porous zirco-
nium trimetaphosphate. Mol Catal 442:107–114. https://doi.org/
10.1016/j.mcat.2017.09.011
33. Xie Y, Wang H, Liu X, Xia Y (2018) Zirconium tripolyphos-
phate as an efcient catalyst for the hydrogenation of ethyl lev-
ulinate to Γ-valerolactone with isopropanol as hydrogen donor.
React Kinet Mech Catal 125:71–84. https://doi.org/10.1007/
s11144-018-1421-1
17. Ooi T, Miura T, Maruoka K (1998) Highly efcient, catalytic
Meerwein–Ponndorf–Verley reduction with a novel bidentate
aluminum catalyst. Angew Chem Int Ed 37:2347–2349. https://
doi.org/10.1002/(SICI)1521-3773(19980918)37:17%3c2347::
AID-ANIE2347%3e3.0.CO;2-U
34. Liu C, Xu G, Hu A et al (2019) Porous zirconium hydroxyphos-
phonoacetate: catalyst for conversion of furfural into furfuryl
alcohol. ChemistrySelect 4:8000–8006. https://doi.org/10.1002/
slct.201901612
18. Srinivasa Rao B, Krishna Kumari P, Koley P et al (2019) One pot
selective conversion of furfural to Γ-valerolactone over zirconia
containing heteropoly tungstate supported on Β-zeolite catalyst.
Mol Catal 466:52–59. https://doi.org/10.1016/j.mcat.2018.12.024
19. Tang X, Hu L, Sun Y et al (2013) Conversion of biomass-derived
ethyl levulinate into γ-valerolactone via hydrogen transfer from
supercritical ethanol over a ZrO2 catalyst. RSC Adv 3:10277–
10284. https://doi.org/10.1039/c3ra41288a
35. Tanay A, Bitincka L, Shamir R et al (2008) Tough, bio-inspired
hybrid materials. Science 322:1516–1521
36. Brewer MS (2011) Natural antioxidants: sources, compounds,
mechanisms of action, and potential applications. Compr Rev
Food Sci Food Saf 10:221–247. https://doi.org/10.1111/j.1541-
4337.2011.00156.x
37. Zhou S, Dai F, Xiang Z et al (2019) Zirconium–lignosulfonate
polyphenolic polymer for highly efcient hydrogen transfer of
biomass-derived oxygenates under mild conditions. Appl Catal B
Environ 248:31–43. https://doi.org/10.1016/j.apcatb.2019.02.011
38. Xu G, Liu C, Hu A et al (2020) A novel synthesis of zirconium
tannate with high stability: new insight into the structure of the
catalyst for hydrogenation. Appl Catal A Gen 602:117666. https://
doi.org/10.1016/j.apcata.2020.117666
20. Yun WC, Yang MT, Lin KYA (2019) Water-born zirconium-based
metal organic frameworks as green and efective catalysts for cata-
lytic transfer hydrogenation of levulinic acid to γ-valerolactone:
critical roles of modulators. J Colloid Interface Sci 543:52–63.
https://doi.org/10.1016/j.jcis.2019.02.036
21. Zhang T, Lu Y, Li W et al (2019) One-pot production of
γ-valerolactone from furfural using Zr-graphitic carbon nitride/
H-β composite. Int J Hydrog Energy 44:14527–14535. https://doi.
org/10.1016/j.ijhydene.2019.04.059
39. Wang X, Hao J, Deng L et al (2020) The construction of novel and
efcient hafnium catalysts using naturally existing tannic acid for
Meerwein–Ponndorf–Verley reduction. RSC Adv 10:6944–6952.
https://doi.org/10.1039/c9ra10317a
22. Li F, France LJ, Cai Z et al (2017) Catalytic transfer hydrogenation
of butyl levulinate to Γ-valerolactone over zirconium phosphates
with adjustable Lewis and BrØnsted acid sites. Appl Catal B Envi-
ron 214:67–77. https://doi.org/10.1016/j.apcatb.2017.05.013
23. Winoto HP, Fikri ZA, Ha JM et al (2019) Heteropolyacid sup-
ported on Zr-Beta zeolite as an active catalyst for one-pot trans-
formation of furfural to Γ-valerolactone. Appl Catal B Environ
241:588–597. https://doi.org/10.1016/j.apcatb.2018.09.031
24. Tang X, Chen H, Hu L et al (2014) Conversion of biomass to
γ-valerolactone by catalytic transfer hydrogenation of ethyl levuli-
nate over metal hydroxides. Appl Catal B Environ 147:827–834.
https://doi.org/10.1016/j.apcatb.2013.10.021
40. Wu J, Ouyang D, He Y et al (2019) Synergistic efect of metal-
organic framework/gallic acid in enhanced laser desorption/ioni-
zation mass spectrometry. ACS Appl Mater Interfaces 11:38255–
38264. https://doi.org/10.1021/acsami.9b11100
41. Leng Y, Shi L, Du S et al (2020) A tannin-derived zirconium-
containing porous hybrid for efcient Meerwein–Ponndorf–Ver-
ley reduction under mild conditions. Green Chem 22:180–186.
https://doi.org/10.1039/c9gc03393a
42. Côté AP, Shimizu GKH (2003) The supramolecular chemistry of
the sulfonate group in extended solids. Coord Chem Rev 245:49–
64. https://doi.org/10.1016/S0010-8545(03)00033-X
25. Xie C, Song J, Zhou B et al (2016) Porous hafnium phosphonate:
novel heterogeneous catalyst for conversion of levulinic acid and
esters into γ-valerolactone. ACS Sustain Chem Eng 4:6231–6236.
https://doi.org/10.1021/acssuschemeng.6b02230
43. Xu G, Liu C, Hu A et al (2019) Transfer hydrogenation of furfural
to furfuryl alcohol over Keggin zirconium-heteropoly acid. Mol
Catal 475:110384. https://doi.org/10.1016/j.mcat.2019.04.013
44. Gilkey MJ, Xu B (2016) Heterogeneous catalytic transfer hydro-
genation as an efective pathway in biomass upgrading. ACS Catal
6:1420–1436. https://doi.org/10.1021/acscatal.5b02171
45. Liu H, Li Y, Jiang H et al (2012) Signifcant promoting efects
of Lewis acidity on Au–Pd systems in the selective oxidation of
aromatic hydrocarbons. Chem Commun 48:8431–8433. https://
doi.org/10.1039/c2cc32024j
26. Xue Z, Liu Q, Wang J, Mu T (2018) Valorization of levulinic
acid over non-noble metal catalysts: challenges and opportunities.
Green Chem 20:4391–4408. https://doi.org/10.1039/c8gc02001a
27. Zhang Y, Yi J, Xu Q (2011) Studies on adsorption of formalde-
hyde in zirconium phosphate–glyphosates. Solid State Sci 13:54–
58. https://doi.org/10.1016/j.solidstatesciences.2010.10.008
28. Zhao X, Zhao Y, Zheng M et al (2019) Efcient separation of vita-
mins mixture in aqueous solution using a stable zirconium-based
metal-organic framework. J Colloid Interface Sci 555:714–721.
https://doi.org/10.1016/j.jcis.2019.08.024
46. Chia M, Dumesic JA (2011) Liquid-phase catalytic transfer
hydrogenation and cyclization of levulinic acid and its esters
to γ-valerolactone over metal oxide catalysts. Chem Commun
47:12233–12235. https://doi.org/10.1039/c1cc14748j
29. Song J, Zhou B, Zhou H et al (2015) Porous zirconium–phytic
acid hybrid: a highly efcient catalyst for Meerwein–Ponndorf–
Verley reductions. Angew Chem Int Ed 54:9399–9403. https://
doi.org/10.1002/anie.201504001
47. Ivanov VA, Bachelier J, Audry F, Lavalley JC (1994) Study of the
Meerwein–Pondorf–Verley reaction between ethanol and acetone
on various metal oxides. J Mol Catal 91:45–59. https://doi.org/10.
1016/0304-5102(94)00017-4
30. Song J, Wu L, Zhou B et al (2015) A new porous Zr-containing
catalyst with a phenate group: an efcient catalyst for the cata-
lytic transfer hydrogenation of ethyl levulinate to γ-valerolactone.
Green Chem 17:1626–1632. https://doi.org/10.1039/c4gc02104e
31. Xue Z, Jiang J, Li G et al (2016) Zirconium-cyanuric acid coordi-
nation polymer: highly efcient catalyst for conversion of levulinic
acid to γ-valerolactone. Catal Sci Technol 6:5374–5379. https://
doi.org/10.1039/c5cy02215k
Publisher’s Note Springer Nature remains neutral with regard to
jurisdictional claims in published maps and institutional afliations.
1 3

X. Li et al.
Authors and Afliations
Xiaoning Li1 · Yehui Li1 · Xiang Wang1 · Haijun Wang1
1
* Haijun Wang
School of Chemical and Material Engineering, Jiangnan
University, Wuxi 214122, China
wanghj@jiangnan.edu.cn
1 3