Metal-free photocatalytic aerobic oxidation of biomass-based furfural derivatives to prepare γ-butyrolactone

Article abstract of DOI:10.1039/d0gc04234j

Efficient catalytic oxidative C-C bond cleavage with dioxygen is useful and challenging to prepare oxygenated fine chemicals from biomass. Herein, we report a catalytic strategy for the preparation of γ-butyrolactone (GBL) by photocatalytic oxidation of tetrahydrofurfuryl alcohol (THFA), tetrahydrofurfuric acid (THFCA), or other furfural derivatives at room temperature under visible-light irradiation. Metal-free mesoporous graphitic carbon nitride was used as the photocatalyst and O₂was used as the oxidant. The effects of various semiconductor catalysts, light sources with different wavelengths, and the reaction time on the photocatalytic oxidation of THFA to GBL were separately investigated. Furthermore, the reaction mechanism was investigated through serious control experiments and the reaction pathway was investigated through density functional theory (DFT) calculations.

Full text of DOI:10.1039/d0gc04234j

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PAPER
Metal-free photocatalytic aerobic oxidation of
biomass-based furfural derivatives to prepare
γ-butyrolactone†
Cite this: Green Chem., 2021, 23,
758
1
Rui Zhu,‡ Gongyu Zhou,‡ Jia-nan Teng, Wanying Liang, Xinglong Li and Yao Fu
*
Efficient catalytic oxidative C–C bond cleavage with dioxygen is useful and challenging to prepare oxyge-
nated fine chemicals from biomass. Herein, we report a catalytic strategy for the preparation of
γ-butyrolactone (GBL) by photocatalytic oxidation of tetrahydrofurfuryl alcohol (THFA), tetrahydrofurfuric
acid (THFCA), or other furfural derivatives at room temperature under visible-light irradiation. Metal-free
2
mesoporous graphitic carbon nitride was used as the photocatalyst and O was used as the oxidant. The
Received 15th December 2020,
Accepted 14th January 2021
effects of various semiconductor catalysts, light sources with different wavelengths, and the reaction time
on the photocatalytic oxidation of THFA to GBL were separately investigated. Furthermore, the reaction
mechanism was investigated through serious control experiments and the reaction pathway was investi-
gated through density functional theory (DFT) calculations.
DOI: 10.1039/d0gc04234j
rsc.li/greenchem
intermediates, perfumes, chemical synthesis and so on. In par-
ticular, GBL is considered as a desirable bio-derived monomer
Introduction
Extensive utilization of fossil resources and the associated for the biopolyester poly(γ-butyrolactone) in the field of poly-
9
environment pollution are well-recognized problems of para- ester materials. Generally, GBL is considered as a key down-
1
10
mount importance in modern society. Developing environ- stream chemical of succinic acid. However, harsh reaction
mentally friendly, renewable alternative resources is of great conditions (such as high temperature and high pressure) are
importance for the renewable production of fine chemicals. the shortcomings of this reaction. Therefore, great efforts still
2
Lignocellulose (cellulose, hemicellulose and lignin), as an need to be made to develop various catalytic strategies for pre-
important biomass resource, has been developed rapidly in paring GBL. The oxidative lactonization of diols, involving
3
recent years. Many platform compounds, such as levulinic sequential oxidation of an alcohol and an intermediate hemia-
4
5
6
11–15
acid (LA), 5-hydroxymethyl furfural (5-HMF), and furfural,
cetal (lactol), is an appealing route to these molecules.
can be obtained by the catalytic conversion of lignocellulose. Numerous stoichiometric oxidants and catalytic methods have
1
1
The preparation of high value-added chemicals through the been explored to achieve this goal.
Aerobic oxidation
catalytic conversion of these platform molecules obtained methods offer a compelling alternative. However, the existing
7
from renewable resources is still the current research focus.
catalysts also face the limitations associated with harsh reac-
Some breakthroughs have also been achieved through the tion conditions, restricted functional group tolerance, and
1
2
efforts of many scientists. Nevertheless, we still need to poor chemoselectivity. In addition to the above methods,
develop much more renewable resource-based reaction strat- GBL can also be prepared by hydrogenation reduction of succi-
1
6
17
egies. This is still of great significance for energy, environ- nic anhydride,
lactonization of hydroxybutyric acid,
1
8
ment, chemicals and other fields. Baeyer–Villiger oxidation of cyclobutanone and catalytic oxi-
8
19
γ-Butyrolactone (GBL), a five-membered ring lactone, is dative C–C bond cleavage of cyclohexanol. Although there
widely used in the fields of material synthesis, pharmaceutical have been many synthesis methods for preparing GBL, it is
still of great significance to develop more synthetic methods to
achieve the efficient and green preparation of GBL.
Hefei National Laboratory for Physical Sciences at the Microscale, iChEM CAS Key
Laboratory of Urban Pollutant Conversion, Anhui Province Key Laboratory of
Biomass Clean Energy, University of Science and Technology of China, Hefei, Anhui,
Recently, organic semiconductor materials have attracted
widespread attention owing to their excellent chemical stabi-
lity and green and efficient photocatalytic properties. In
20
230026, P. R. China. E-mail: fuyao@ustc.edu.cn
addition, they also have a suitable band gap between the
†
Electronic supplementary information (ESI) available. See DOI: 10.1039/
2
1
valence and conduction bands, which provides the possi-
bility for oxidation or reduction of many substrates. Recently,
d0gc04234j
These authors contributed equally to this work.
‡
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scientists have developed various catalytic systems based on a nitrogen atmosphere. Subsequently, hydrofluoric acid was
organic semiconductor materials driven by the demand for used to remove SiO . Then, the obtained pale-yellow solid was
2
green and sustainable chemistry. Among various organic semi- washed with water and ethanol several times and dried at
conductor materials, mesoporous graphitic carbon nitride is 80 °C for about 12 h. A pale-yellow solid (about 4 g) was finally
2
2
23
widely used in water splitting, selective oxidation and obtained and denoted as M-CNU.
2
4
photoredox catalytic organic transformations
of organic
Other semiconductor materials (such as TiO
2 3 2
, WO , MoS ,
molecules because of its facile synthesis and excellent photo- CdS, and Al
2 3
O
) were purchased and used directly without any
catalytic reactivity. The properties of large surface area, plenty further treatment in this work.
of vacancies and high photocatalytic activity all make meso-
Preparation of 2,5-dihydroxymethyltetrahydrofuran and
tetrahydrofurandicarboxylic acid
porous graphitic carbon nitride a promising catalyst for many
reactions.
In this manuscript, we reported a catalytic strategy for the 2,5-Dihydroxymethyltetrahydrofuran was prepared from
preparation of γ-butyrolactone (GBL) by photocatalytic oxi- 5-hydroxymethylfurfural (5-HMF) by hydrogenation experi-
2
5
30
dation of tetrahydrofurfuryl alcohol (THFA), tetrahydrofurfu- ments. A 25 mL stainless steel autoclave with a stir bar was
2
6
27
ric acid (THFCA), or other furfural derivatives at room charged with 1.8 g of 5-HMF, RANEY® nickel catalyst (100 mg)
temperature under visible-light irradiation (as shown in and 10 mL of ethanol. The stainless steel autoclave was purged
Scheme 1). Metal-free M-CNU (mesoporous graphitic carbon 3 times with nitrogen and 2 times with hydrogen. Then the
nitride, prepared from urea) was used as the photocatalyst and autoclave was pressurized to 5 MPa with hydrogen and heated
2 2
O (O balloon or air) was used as the oxidant. We separately to 120° C for 3 hours. After cooling, the stainless steel auto-
investigated the effects of various semiconductor catalysts, clave was vented and the solids were separated by filtration.
light sources with different wavelengths, and the reaction time The acetic acid solution was evaporated under vacuum to
on the photocatalytic oxidation of THFA to GBL. Furthermore, provide about 1.5 g of 2,5-dihydroxymethyltetrahydrofuran.
we also investigated the reaction mechanism through serious
Tetrahydrofuran-2,5-dicarboxylic acid was prepared from
control experiments and the reaction pathway was further furan-2,5-dicarboxylic acid (FDCA) by hydrogenation experi-
investigated through density functional theory (DFT) ments. A 25 mL autoclave with a stir bar was charged with
calculations.
2.0 g of furan-2,5-dicarboxylic acid (FDCA), 0.1 g of 10% Pd/C
and 10 mL of acetic acid. The autoclave was purged 3 times
with nitrogen and 2 times with hydrogen. Then the autoclave
was pressurized to 4 MPa with hydrogen and heated to 150° C
for 3 hours. After cooling, the autoclave was vented and the
solids were separated by filtration. The acetic acid solution was
evaporated under vacuum to provide about 1.6 g of tetrahydro-
furan-2,5-dicarboxylic acid.
Experimental
Preparation of graphitic carbon nitride
Graphitic carbon nitride was synthesized according to a pre-
2
8
vious work. Briefly, about 40 g urea or melamine was directly
−
1
heated at 550 °C for 4 h (heating rate: 2.5 °C min ) under a
nitrogen atmosphere, giving a pale-yellow solid denoted as General procedure for photocatalytic reactions
CNU or CNM respectively.
To a 10 mL reaction tube with a stir bar were added the sub-
Mesoporous graphitic carbon nitride was synthesized
according to a previous work. Briefly, about 40 g urea was
dissolved in a solution of 0.2 M HCl (60 mL) and ethanol
strate (0.4 mmol) and then 10 mg catalyst. Subsequently, 1 mL
MeCN was added as the solvent. The reaction mixture was
stirred for 12 h at room temperature under a 390 nm light
source at 1 atm O pressure (O balloon). The conversion and
2
9
(
(
52 mL) under vigorous stirring, and tetraethyl orthosilicate
32 mL) was then slowly added to the above solution drop by
2
2
yield were determined by GC with diphenyl as the internal
standard. The conversion of the substrate and the product
yield were calculated according to the following formula:
drop. After stirring vigorously at room temperature for 3 h, the
mixture was heated under vacuum for solvent evaporation and
then dried at 100 °C for about 12 h. The obtained white solid
was heated at 550 °C for 4 h (heating rate: 2.5 °C min− ) under
1
Conversion ¼ ðn0 ꢀ n1Þ=n0 ꢁ 100%
Yield ¼ nðactual yieldÞ=nðtheoretical yieldÞ ꢁ 100%
where n
0 1
is mol of the substrate before reaction and n is mol
of the substrate after reaction.
The apparent quantum efficiency (QE) was measured under
the same photocatalytic reaction conditions. The QE was calcu-
3
1
lated according to the following formula:
Number of reacted electrons
Number of incident electrons
QE ¼
ꢁ 100%
Number of target products
Number of incident electrons
Scheme 1 The strategy for the photocatalytic oxidation of furfural
derivatives to prepare GBL.
¼
ꢁ 100%
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General information for DFT calculations
carbon nitride has a larger redox window range than most
semiconductors. Furthermore, the used light source could also
match the band gap of carbon nitride (entries 8–10) and the
UV-Vis absorption spectra (as shown in Fig. S2†) of various
semiconductor materials were able to prove this point. In
addition, it seemed that different precursors may also affect
the activity of carbon nitride. Better conversion and yield were
obtained for reactions performed with the catalyst of M-CNU,
possibly due to its higher specific surface area with much
more active sites. Therefore, we separately characterized the
physicochemical properties of different carbon nitrides to
verify the above conjecture. As presented in Table 2, the
specific surface areas of CNM, CNU and M-CNU were 18.3,
3
2
The Gaussian 16 package was used for all DFT calculations.
3
3,34
35
The B3LYP functional
and 6-31G*
basis set were
employed for geometry optimization of the catalyst, reactants,
intermediates, and products. Vibrational frequencies were
then calculated at the same level used to obtain zero-point
energy (ZPE) corrections. For each transition state, only one
imaginary frequency was found, whereas no imaginary fre-
quencies were found for all the reactants, intermediates, and
products. Afterward, intrinsic reaction coordinate (IRC) ana-
lysis was conducted.
2
−1
5
5.4 and 215.1 m g , respectively, according to the N physi-
2
cal adsorption results, verifying the above conjecture. The
larger specific surface area of M-CNU was mainly attributed to
Results and discussion
In order to test the photocatalytic reaction of THFA, various the mesoporous structure (Fig. 1) of the catalyst. In addition,
heterogeneous semiconductor materials were used as the cata- the UV-Vis absorption of the catalysts was further investigated.
lysts initially. The results of various catalysts under identical As shown in Fig. 2a, CNM, CNU and M-CNU all had good
reaction conditions are presented in Table 1. When there was absorbance at wavelengths ranging from 300 to 400 nm. The
no catalyst in the reaction system, THFA was not converted band gaps of CNM, CNU, and M-CNU were calculated to be
(
entry 1). When typical semiconductors were used as the 2.6, 2.7, and 2.6 eV, respectively, according to the Kubelka–
3
7
2 3 2
photocatalysts, such as TiO , WO , MoS , CdS and so on (as Munk plot. Thus, the light absorptions of these three carbon
presented in Table 1, entries 2–7), they exhibited low reactivity nitrides were all excellent, and this result demonstrated that
for this reaction. When CNM (carbon nitride, prepared from
melamine) was used as the catalyst, it exhibited relatively high
catalytic activity, with 50% conversion and 44% yield. When
CNU (carbon nitride, prepared from urea) was used as the cata-
lyst, 57% conversion and 51% yield could be obtained. When
M-CNU (mesoporous graphitic carbon nitride) was used as the Entry
Table 2
2
N physical adsorption results of CNM, CNU and M-CNU
Sample
S
BET (m g−1)
a
2
V
pore (cm g−1)
3
dpore (nm)
b
catalyst, 72% conversion and 64% yield could be obtained.
1
2
3
CNM
CNU
M-CNU
18.3
55.4
215.1
0.15
0.32
0.81
3.4
3.8
8.7
Based on the above experimental results, we speculated that
the conversion from THFA to GBL was mainly dependent on
the oxidizing power of the valence band and the absorbance of
a
b
Multipoint BET surface area. Cumulative volume of pores and
3
6
the semiconductor materials. According to a previous report,
average pore width determined by the BJH method.
a
Table 1 The photocatalytic oxidation of THFA to GBL with different catalysts
c
Entry
Catalyst
Solvent
t [h]
Light sources
Conversion
Yield
1
2
3
4
5
6
7
8
9
—
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
3
3
3
3
3
3
3
3
3
3
CN
CN
CN
CN
CN
CN
CN
CN
CN
CN
10
10
10
10
10
10
10
10
10
10
10
390 nm
390 nm
390 nm
390 nm
390 nm
390 nm
390 nm
390 nm
390 nm
390 nm
390 nm
Trace
<5%
<5%
34%
7%
<5%
20%
50%
57%
72%
—
N.D.
<5%
Trace
31%
5%
<5%
12%
44%
51%
64%
Fe
Al
TiO
2
O
3
2
O
3
2
WO
MoS
CdS
CNM
CNU
M-CNU
M-CNU
3
2
1
1
0
1
b
Neat
0.21 mmol
a
b
Reaction conditions: 0.4 mmol THFA, 10 mg catalyst, 1 mL MeCN, 390 nm LED, O balloon, room temperature, and 10 h. Reaction conditions:
2
c
1
mL THFA, 10 mg catalyst, 390 nm LED, O
2
balloon, room temperature, and 10 h. Yields were determined by gas chromatography (GC) analysis
using biphenyl as the internal standard.
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Fig. 1 SEM (a) and TEM (b) images of the M-CNU catalyst.
Fig. 2 UV-Vis patterns (a) and photoluminescence spectra (b) of CNM, CNU and M-CNU. Inset in (a) shows a digital photograph and the plot of the
transformed Kubelka–Munk function versus the photoenergy for CNM, CNU and M-CNU samples.
the UV-Vis absorption of these three catalysts contributed little Therefore, low photoluminescence intensity was another factor
to the catalytic reactivity differences.
affecting the catalytic performance on the transformation of
We also characterized the XRD patterns of the as-prepared THFA into GBL. In addition, we also tried to use solvent-free
carbon nitrides. As shown in Fig. S7,† two typical diffraction reaction conditions, and about 0.21 mmol (corresponding to a
peaks around 12.9° and 27.7°corresponded to the intralayer generation efficiency of 2.1 mmol gcat.−
1
h
−1
) GBL could be
long-range order and the interlayer periodic stacking which obtained under the same reaction conditions. The effect of the
3
8
was controlled by van der Waals forces, respectively.
reaction time on the photocatalytic oxidative cleavage of THFA
According to a previous report, the weak peak of the intralayer to prepare GBL was investigated under the optimal reaction
long-range order indicated that CNU and M-CNU had less conditions. The mole amount of GBL at different times within
intralayer hydrogen bonds, showing superior photoactivity 50 hours was determined respectively. The corresponding pro-
3
9
because of the fast charge transfer between interlayers.
duction efficiency of GBL was also calculated. As shown in
Besides, the relatively weak and broadened peaks at 27.7° of Fig. 3, there was almost a linear relationship between the mole
CNU and M-CNU indicated that the polymerization of urea amount of GBL and the reaction time. It was worth mention-
gave the carbon nitride structure with less layers. Moreover, ing that the production efficiency of GBL was stable, about
photoluminescence spectra of these three carbon nitrides were 2.2 mmol gcat.−
1
h . Based on the above experimental results,
−1
also investigated. As shown in Fig. 2b, M-CNU has the lowest we could draw the conclusion that carbon nitride was relatively
electron–hole recombination rate according to the low photo- stable under these reaction conditions and could still have
luminescence intensity compared with CNM and CNU. good reactivity after working for 50 hours. In addition, the
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Fig. 3 The effect of the reaction time on the photocatalytic oxidation
of THFA to GBL. Reaction conditions: 1 mL THFA, 10 mg catalyst,
2
390 nm LED, O balloon, and room temperature. Yields were deter-
mined by gas chromatography (GC) analysis using biphenyl as the
internal standard.
recyclability test of this catalyst was performed for five con-
secutive runs and the detailed experimental process is shown
in the ESI.† As shown in Fig. S3,† the product yield was slightly
reduced and this was mainly caused by the loss of the catalyst
during the catalyst transfer process. The catalyst loss was
about 3–6 wt% after each recovery. In addition, we performed
XRD, XPS and SEM of the fresh catalyst (M-CNU) and the
recovered catalyst respectively. The XRD (Fig. S4†) and SEM
Scheme 2 Validation experiments and other substrates.
(Fig. S5†) results both confirmed the stability of the catalyst
morphology. The XPS results (Fig. S6†) showed that the chemi-
cal valence states of C and N did not change significantly. In under the same reaction conditions. The corresponding target
summary, the stable product yields observed herein and the product was succinic anhydride with the byproduct of succinic
characterization results of the catalyst indicated that the cata- acid.
lysts could be recycled and reused several times.
In addition, to identify the roles of different oxidative
Validation experiments were performed under optimal reac- species in the photocatalytic oxidation of THFA to GBL, a
tion conditions (as shown in Scheme 2) to investigate the reac- series of experiments were carried out with different sacrificial
1
•
tion mechanism. As a comparison, nitrogen was used as the agents, such as tryptophan for O , p-phthalic acid for OH, KI
2
•
+
− 40
protective gas for the reaction (entry a). Low conversion and for h and p-benzoquinone for O
2
.
As compared to the
trace GBL could be detected in this reaction system. On the experiment without a sacrificial agent, the yield of GBL
basis of the above result, it could be concluded that oxygen decreased obviously when KI or p-benzoquinone was used as
was essential to the preparation of GBL from the photocatalytic the sacrificial agent and the yield of GBL varied little when
oxidative cleavage of THFA. Additionally, in order to clarify tryptophan or p-phthalic acid was used as the sacrificial agent.
that the H atom on the hydroxyl group was activated by the Additionally, electron paramagnetic resonance (EPR) experi-
catalyst resulting in the C–C cleavage, tetrahydrofurfuryl ments were performed to confirm the active species of oxygen
•
−
acetate was used as the substrate (entry b). The trace target (Fig. 4). O
2
was confirmed using 5,5-dimethyl-1-pyrroline
product was obtained through the analysis of the reaction N-oxide (DMPO) as the spin trapper. No EPR signal was
solution, indicating that the activation of the hydroxyl group detected without light irradiation, consistent with the above
was crucial for this reaction. Another interesting finding was experimental result (Table 3, entry 7). In addition, the possible
that the H atom of the carboxyl group could also be activated reactions for the active oxygen species using carbon nitrides
in the same catalytic system, and about 85% of GBL was are given as follows (Scheme 3).
obtained resulting from the decarboxylation oxidation. It
When incident light irradiates the surface of carbon
seemed that the C–C bond of THFCA was more prone to clea- nitrides, electrons in the valence band of the photocatalyst will
vage than that of THFA. In addition, tetrahydrofurandimetha- be excited to transition to the conduction band, and the
nol and tetrahydrofurandicarboxylic acid, as furanyl deriva- corresponding holes will be left in the valence band of the
4
1
tives, could also be cleaved by photocatalytic aerobic oxidation photocatalyst. Photogenerated electrons and holes are effec-
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Scheme 3 The possible mechanism of active oxygen species.
tively separated. At this time, oxygen is reduced by the excited
electrons from the conduction band to generate a superoxide
•
−
42
+
radical anion (O
2
), and THFA could be transformed into H
Fig. 4 Detection of the superoxide radical (O
M-CNU using the spin-trap method.
2
•−) formed by irradiated and alkoxy radicals in the valence band. The superoxide
+
•
radical anion could be combined with H to generate OOH.
The results obtained from the above experiments indicated
that this catalytic strategy afforded an efficient protocol for the
transformation of THFA into GBL. Some mechanisms, invol-
ving the C–C bond cleavage of cyclic alcohols or vicinal diols
Table 3 The photocatalytic oxidation of THFA to GBL with different
light sources
Time Light
Entry Catalyst [h] source
Yield
Yield
AQE via proton-coupled electron-transfer activation of alcohol O–H
[mmol] [mmol g− h−1
1
]
[%]
43
bonds, were even proposed. To further shed light on the reac-
1
2
3
4
5
6
7
M-CNU
M-CNU
M-CNU
M-CNU
M-CNU
M-CNU
M-CNU
10
10
10
10
10
10
10
467 nm 0.14
456 nm 0.2
440 nm 0.23
427 nm 0.28
390 nm 0.21
370 nm 0.08
1.4
2.0
2.3
2.8
2.1
0.8
—
0.9
0.8
0.9
1.3
2.7
1.9
—
tion mechanism, extensive density functional theory (DFT) cal-
culations were performed (as shown in Scheme 4) sub-
sequently. Initially, we ruled out direct excitation pathways due
to the observation that there was no spectral overlap between
the emission of the 390 nm LEDs and the absorption of THFA.
The excitation of THFA might have two possibilities in this
Dark
Trace
Reaction conditions: Substrate 1 mL, neat, O
2
balloon, catalyst 10 mg, carbon nitride catalyzed photosystem. One was the direct acti-
and room temperature. The result was obtained by GC with biphenyl
as the internal standard.
vation of the hydroxyl group through abstracting a hydrogen
by carbon nitride, yielding an alkoxy radical intermediate 2
Scheme 4 Energy profiles for the proposed reaction mechanism.
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Path I). The other one was the loss of Chydroxyl-H through a
transition state TS1, with the carbon radical 7 generated. After
an intramolecular hydrogen transfer reaction via TS2, THFA
can also be transformed into the alkoxy radical intermediate 2
Green Chemistry
(
Notes and references
1 (a) J. Tollefson, Reality check for fossil-fuel divestment,
Nature, 2015, 521, 16–17; (b) N. Fabian, Economics:
support low-carbon investment, Nature, 2015, 519, 27–29;
(c) J. Tollefson, Can the world kick its fossil-fuel addiction
fast enough?, Nature, 2018, 556, 422–425; (d) Q. Di,
Y. Wang, A. Zanobetti, Y. Wang, P. Koutrakis, C. Choirat,
F. Dominici and J. D. Schwartz, Air Pollution and Mortality
in the Medicare Population, N. Engl. J. Med., 2017, 376,
2513–2522.
(Path II). The alkoxy radical makes the adjacent C–C bond
unstable, which then breaks spontaneously to form the carbon
radical 3 and a molecule of HCHO. Later, the product from
•
oxygen activation ( OOH) by carbon nitride can combine with
3
, forming a stable compound 4, which transformed into the
final product GBL after losing a molecule of water. Three path-
ways for the dehydration of 4 might occur. In Path I, as the O–
O bond in 4 is unstable, it might be cleaved directly to form a
hydroxyl radical and the oxygen radical intermediate 5. Then
radical 5 would further lose a hydrogen to form GBL. Also,
intermediate 4 might be converted into GBL in one step via
different intramolecular dehydration reactions (Paths III and
IV). From the energy profile, Path I was the most favorable
pathway due to its lowest activation energy.
2 T. László, E. C. Mika and Á. Németh, Chem. Rev., 2018, 118,
505–613.
3 (a) R.-J. van Putten, J. C. van der Waal, E. de Jong,
C. B. Rasrendra, H. J. Heeres and J. G. de Vries, Chem. Rev.,
2013, 113(3), 1499–1597; (b) I. Delidovich, P. J. C. Hausoul,
L. Deng, R. Pfützenreuter, M. Rose and R. Palkovits, Chem.
Rev., 2016, 116(3), 1540–1599.
4
S. G. Wettstein, D. M. Alonso, Y. Chong and J. A. Dumesic,
Energy Environ. Sci., 2012, 5, 8199–8203.
Conclusions
5 E. Nikolla, Y. Román-Leshkov, M. Moliner and M. E. Davis,
ACS Catal., 2011, 1(4), 408–410.
In summary, we have developed a heterogeneous metal-free
photocatalytic strategy to achieve the preparation of GBL with
biomass-based furfural derivatives under ambient conditions.
Mesoporous graphitic carbon nitride is used as the photo-
6
X. Li, P. Jia and T. Wang, ACS Catal., 2016, 6(11), 7621–
640; R. Mariscal, P. Maireles-Torres, M. Ojeda, I. Sádaba
and M. L. Granados, Energy Environ. Sci., 2016, 9, 1144–
189.
7
1
catalyst and O is used as the oxidant without any other addi-
2
7
M. Hara, K. Nakajima and K. Kamata, Sci. Technol. Adv.
Mater., 2015, 16, 034903.
tives under visible-light irradiation. Efficient preparation of
GBL could be achieved with this catalytic strategy under neat
reaction conditions. In addition, serious control experiments
and DFT calculations were adopted to illustrate the possible
reaction mechanism. The generation of the alkoxy radical
intermediate is essential for the cleavage of the C–C bond, and
the superoxide radical anion has been proven to be the reactive
oxygen species for this reaction. In this manuscript, we
expanded the photocatalytic conversion path of biomass
resources and first realized the photocatalytic synthesis of GBL
from biomass-based furfural derivatives.
8
9
X. Li, X. Lan and T. Wang, Green Chem., 2016, 18, 638–642.
(a) M. Hong and E. Y.-X. Chen, Nat. Chem., 2016, 8, 42–49;
(
b) Y. Shen, J. Zhang, N. Zhao, F. Liu and Z. Li, Polym.
Chem., 2018, 9, 2936–2941.
1
0 (a) L. Corbel-Demailly, B. Ly, D. Minh, B. Tapin, C. Especel,
F. Epron, A. Cabiac, E. Guillon, M. Besson and C. Pinel,
ChemSusChem, 2013, 6, 2388–2395; (b) K. H. Kang,
U. G. Hong, Y. Bang, J. H. Choi, J. K. Kim, J. K. Lee,
S. J. Han and I. K. Song, Appl. Catal., A, 2015, 490, 153–162;
(c) T. J. Korstanje, J. I. van der Vlugt, C. J. Elsevier and B. de
Bruin, Science, 2015, 350, 298–302; (d) Y. Takeda,
M. Tamura, Y. Nakagawa, K. Okumurab and K. Tomishige,
Catal. Sci. Technol., 2016, 6, 5668–5683; (e) K. H. Kang,
S. J. Han, J. Won-Lee, T. H. Kim and I. K. Song, Appl. Catal.,
A, 2016, 524, 206–213; (f) M. A. Hamdana, S. Loridanta,
M. Jahjahb, C. Pinela and N. Perret, Appl. Catal., A, 2019,
Conflicts of interest
The authors declare no conflicts of interest.
571, 71–81.
Acknowledgements
1
1 (a) M. C. Bagley, Z. Lin, D. J. Phillips and A. E. Graham,
Tetrahedron Lett., 2009, 50, 6823–6825; (b) T. M. Hansen,
G. J. Florence, P. Lugo-Mas, J. Chen, J. N. Abrams and
C. J. Forsyth, Tetrahedron Lett., 2003, 44, 57–59.
This work was supported by the National Natural Science
Foundation of China (21572212, 51821006, and 51961135104),
the National Key R&D Program of China (2018YFB1501604),
the Major Science and Technology Projects of Anhui Province 12 (a) H. Shimizu, S. Onitsuka, H. Egami and T. Katsuki,
(
18030701157), the Users with Excellence Program of Hefei
J. Am. Chem. Soc., 2005, 127, 5396–5413; (b) T. Mitsudome,
A. Noujima, T. Mizugaki, K. Jitsukawa and K. Kaneda,
Green Chem., 2009, 11, 793–797; (c) K. Chung, S. M. Banik,
A. G. De Crisci, D. M. Pearson, T. R. Blake, J. V. Olsson,
A. J. Ingram, R. N. Zare and R. M. Waymouth, J. Am. Chem.
Soc., 2013, 135, 7593–7602; (d) T. R. Blake and
Science Center CAS (Grant 2019HSC-UE017), the Strategic
Priority Research Program of the CAS (XDA21060101). The
authors thank Hefei Leaf Biotech Co., Ltd and Anhui Kemi
Machinery Technology Co., Ltd for free samples and equip-
ment that benefited their ability to conduct this study.
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Paper
R. M. Waymouth, J. Am. Chem. Soc., 2014, 136, 9252–9255; 24 A. Savateev, I. Ghosh, B. König and M. Antonietti, Angew.
e) A. Díaz-Rodríguez, I. Lavandera, S. Kanbak-Aksu, Chem., Int. Ed., 2018, 57, 15936–15947.
R. A. Sheldon, V. Gotor and V. Gotor-Fernández, Adv. Synth. 25 Z. Wu, J. Wang, S. Wang, Y. Zhang, G. Bai, L. Ricardez-
(
Catal., 2012, 354, 3405–3408.
3 X. Xie and S. S. Stahl, J. Am. Chem. Soc., 2015, 137, 3767–
Sandoval, G. Wang and B. Zhao, Green Chem., 2020, 22,
1432–1442.
1
1
1
3
770.
26 T. Asanoa, Y. Nakagawaab, M. Tamurac and K. Tomishige,
Appl. Catal., A, 2020, 602, 117723.
27 (a) J. J. Wiesfeld, M. Kim, K. Nakajima and E. J. M. Hensen,
Green Chem., 2020, 22, 1229–1238; (b) L. Wei, J. Zhang,
W. Deng, S. Xie, Q. Zhang and Y. Wang, Chem. Commun.,
2019, 55, 8013–8016.
4 C. Zhu, Q. Li, L. Pu, Z. Tan, K. Guo, H. Ying and P. Ouyang,
ACS Catal., 2016, 6, 4989–4994.
5 (a) T. Mitsudome, A. Noujim, T. Mizugaki, K. Jitsukawaa
and K. Kaneda, Green Chem., 2009, 11, 793–797;
(b) S. Musa, I. Shaposhnikov, S. Cohen and D. Gelman,
Angew. Chem., Int. Ed., 2011, 50, 3533–3537; (c) P. Könst, 28 M. M. C. H. van Schie, W. Zhang, F. Tieves, D. S. Choi,
S. Kara, S. Kochius, D. Holtmann, I. W. C. E. Arends,
R. Ludwig and F. Hollmann, ChemCatChem, 2013, 5, 3027–
C. B. Park, B. O. Burek, J. Z. Bloh, I. W. C. E. Arends,
C. E. Paul, M. Alcalde and F. Hollmann, ACS Catal., 2019,
9(8), 7409–7417.
3
032; (d) X. Li, Y. Cui, X. Yang, W. Dai and K. Fan, Appl.
Catal., A, 2013, 458, 63–70; (e) Y. Ryabenkova, 29 L. Shi, L. Liang, F. X. Wang, M. S. Liu, K. L. Chen,
P. J. Miedziak, D. W. Knight, S. H. Taylor and
G. J. Hutchings, Tetrahedron, 2014, 70, 6055–6058;
K. N. Sun, N. Q. Zhang and J. M. Sun, ACS Sustainable
Chem. Eng., 2015, 3, 3412–3419.
(
f) S. Chakraborty, P. O. Lagaditis, M. Förster, 30 T. Buntara, S. Noel, P. H. Phua, I. Melián-Cabrera, G. de
E. A. Bielinski, N. Hazari, M. C. Holthausen, W. D. Jones
and S. Schneider, ACS Catal., 2014, 4, 3994–4003;
Vries and H. J. Heeres, Angew. Chem., Int. Ed., 2011, 50,
7083–7087.
(
g) K. Paudel, B. Pandey, S. Xu, D. K. Taylor, D. L. Tyer, 31 J. Yu, J. Zhang and M. Jaroniec, Green Chem., 2010, 12,
C. L. Torres, S. Gallagher, L. Kong and K. Ding, Org. Lett.,
1611–1614.
2
018, 20, 4478–4481.
32 Gaussian 16, Revision A.01, Gaussian Inc., Wallingford, CT,
1
1
6 (a) S. A. Regenhardt, C. I. Meyer, T. F. Garetto and
A. J. Marchi, Appl. Catal., A, 2012, 449, 81–87; (b) R. Li, 33 A. D. Becke, Phys. Rev. A: At., Mol., Opt. Phys., 1988, 38,
2016.
J. Zhao, D. Han and X. Li, Chin. Chem. Lett., 2017, 28,
330–1335.
3098.
1
34 A. D. Becke, J. Chem. Phys., 1993, 98, 1372–1377.
7 M. T. Pérez-Prior, J. A. Manso, M. P. García-Santos, 35 R. Krishnan, J. S. Binkley, R. Seeger and J. A. Pople,
E. Calle and J. Casado, J. Org. Chem., 2005, 70, 420–
26.
8 M. E. González-Núñez, R. Mello, A. Olmos and G. Asensio,
J. Org. Chem., 2005, 70, 10879–10882.
9 C. Xiao, Z. Du, S. Li, Y. Zhao and C. Liang, ChemCatChem,
J. Chem. Phys., 1980, 72, 650–654.
4
36 I. Ghosh, J. Khamrai, A. Savateev, N. Shlapakov,
M. Antonietti and B. König, Science, 2019, 365, 360–366.
37 Q. Wu, Y. M. He, H. L. Zhang, Z. Y. Feng, Y. Wu and
T. H. Wu, Mol. Catal., 2017, 436, 10–18.
1
1
2
2
020, 12, 3650–3655.
38 Y. Kang, Y. Yang, L.-C. Yin, X. Kang, L. Wang, G. Liu and
H.-M. Cheng, Adv. Mater., 2016, 28, 6471–6477.
0 (a) F. Parrino, M. Bellardita, E. I. García-López, G. Marcì,
V. Loddo and L. Palmisano, ACS Catal., 2018, 8, 11191– 39 M. Shalom, S. Inal, D. Neher and M. Antonietti, Catal.
1225; (b) T. Chhabra, A. Bahuguna, S. S. Dhankhar, Today, 2014, 225, 185–190.
C. M. Nagaraja and V. Krishnan, Green Chem., 2019, 21, 40 J. Ma, D. Jin, Y. Li, D. Xiao, G. Jiao, Q. Liu, Y. Guo, L. Xiao,
1
6
012–6026; (c) S. Dhingra, T. Chhabra, V. Krishnan and
C. M. Nagaraja, ACS Appl. Energy Mater., 2020, 3, 7138–
148.
X. Chen, X. Li, J. Zhou and R. Sun, Appl. Catal., B, 2021,
283, 119520.
41 A. Kudo and Y. Miseki, Chem. Soc. Rev., 2009, 38, 253–278.
7
2
1 (a) X. Wang, K. Maeda, A. Thomas, K. Takanabe, G. Xin, 42 F. Su, S. C. Mathew, G. Lipner, X. Fu, M. Antonietti,
J. M. Carlsson, K. Domen and M. Antonietti, Nat. Mater.,
009, 8, 76–80; (b) Y. Wang, X. Wang and M. Antonietti,
S. Blechert and X. Wang, J. Am. Chem. Soc., 2010, 132,
16299–16301.
2
Angew. Chem., Int. Ed., 2012, 51, 68–89.
2 G. Liao, Y. Gong, L. Zhang, H. Gao, G. Yang and B. Fang,
Energy Environ. Sci., 2019, 12, 2080–2147.
3 L. Luo, T. Zhang, M. Wang, R. Yun and X. Xiang,
ChemSusChem, 2020, 13, 5173–5184.
43 (a) A. Hu, Y. Chen, J. Guo, N. Yu, Q. An and Z. Zuo, J. Am.
Chem. Soc., 2018, 140, 13580–13585; (b) E. Ota, H. Wang,
N. L. Frye and R. R. Knowles, J. Am. Chem. Soc., 2019, 141,
1457–1462; (c) R. Zhu, G. Zhou, J. Teng, X. Li and Y. Fu,
ChemSusChem, 2020, 13, 5248–5255.
2
2
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