Vanadium Oxide-Nitride Composites for Catalytic Oxidative C?C Bond Cleavage of Cyclohexanol into Lactones with Dioxygen

Article abstract of DOI:10.1002/cctc.202000288

Selective catalytic oxidative C?C bond cleavage with dioxygen is useful and challenging to prepare oxygenated fine chemicals. Herein we fabricated vanadium oxide–nitride composites as catalysts via a facile thermal treatment process, and the surface composition could be tuned by the thermal treatment temperature, which could affect catalytic oxidation of cyclohexanol significantly. By using such a V?N?C composite prepared at 500 °C, cyclohexanol could be selectively oxidized with dioxygen into lactones including δ-valerolactone and γ-butyrolactone, rather than common dicarboxylic acids. Cyclohexanone and 2-cyclohexen-1-one were verified as two key intermediates. V³⁺ species in the form of vanadium nitride and vanadium (III) oxide were detected, and well dispersed on amorphous carbon with a low degree of graphitization. These findings will provide a reference for catalytic oxidative C?C bond cleavage with molecular oxygen under mild reaction conditions.

Full text of DOI:10.1002/cctc.202000288

Communications
doi.org/10.1002/cctc.202000288
ChemCatChem
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
Vanadium Oxide-Nitride Composites for Catalytic Oxidative
CÀ C Bond Cleavage of Cyclohexanol into Lactones with
Dioxygen
[a, b]
[a, b]
[b]
[b]
[a, b]
Chuhong Xiao,
Zhongtian Du,*
Shaojie Li, Yanbin Zhao, and Changhai Liang*
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
Selective catalytic oxidative CÀ C bond cleavage with dioxygen
is useful and challenging to prepare oxygenated fine chemicals.
Herein we fabricated vanadium oxide–nitride composites as
catalysts via a facile thermal treatment process, and the surface
composition could be tuned by the thermal treatment temper-
ature, which could affect catalytic oxidation of cyclohexanol
significantly. By using such a VÀ NÀ C composite prepared at
valerolactone (DVL) have good mechanical properties, hydro-
[10]
lysability, and biocompatibility. Great efforts have been made
to develop a variety of synthetic procedures for lactones. Three
typical methods are often used for the synthesis of such cyclic
intramolecular esters depending on different feedstocks
(Scheme 1): (1) Baeyer-Villiger oxidation of ketones with
[
11]
[12]
peroxides; (2) oxidative lactonisation of diols; (3) selective
[
13]
5
00°C, cyclohexanol could be selectively oxidized with dioxy-
reduction of carboxylic acids and their derivatives.
The
gen into lactones including δ-valerolactone and γ-butyrolac-
tone, rather than common dicarboxylic acids. Cyclohexanone
and 2-cyclohexen-1-one were verified as two key intermediates.
economic and environmental factors of these synthetic meth-
ods rely heavily on the starting materials and the related
technical routes. It is rather attractive to develop novel methods
for preparation of lactones, especially using inexpensive feed-
stocks.
3
+
V
species in the form of vanadium nitride and vanadium (III)
oxide were detected, and well dispersed on amorphous carbon
with a low degree of graphitization. These findings will provide
a reference for catalytic oxidative CÀ C bond cleavage with
molecular oxygen under mild reaction conditions.
6
The mixture of cyclohexanol/cyclohexanone (KA oil, 6×10
tons per year), is an important industrial raw material for the
[14]
production of caprolactam and adipic acid. Oxidation of KA
oil into adipic acid is usually performed with stoichiometric
nitric acid in industry, which would generate a large amount of
[14,15]
NOx.
Meanwhile catalytic oxidation of KA oil with molecular
CÀ C bond is one of the most fundamental chemical bonds in
organic molecules. Carbonyl groups could be generated
through oxidative cleaving CÀ C bond, which would be useful in
the fields such as synthesis of oxygenated fine chemicals,
degradation of polymers and breakdown of lignocellulose
oxygen generally results in a mixture of dicarboxylic acids,
which is unfavourable. However, few reports are disclosed for
oxidation of cyclohexanol or cyclohexanone into intermediate
oxygenates like lactones. The oxidative CÀ C bond cleavage is
an effective approach to produce cyclic intramolecular esters by
inserting oxygen atoms into cyclic compounds. We are
interested in catalytic selective oxidation of cyclohexanol or
cyclohexanone with molecular oxygen into lactones like γ-
butyrolactone and δ-valerolactone, rather than dicarboxylic
acids.
[1–5]
etc.
Due to high bond dissociation energies (BDEs) of CÀ C
bonds (75–118 kcal/mol) as well as the inert molecular oxygen
[5]
at the ground state, selective catalytic oxidative CÀ C bond
cleavage with molecular oxygen under mild reaction conditions
is rather attractive and challenging from both academic and
[6–8]
industrial perspectives.
As a kind of abundant and non-precious metal, vanadium
has a variety of chemistry, and is widely used in the field of
Lactones are important fine chemicals with a wide range of
applications in industry, including pharmaceutical ingredients,
[6,16,17]
catalytic oxidation.
e.g., vanadium phosphorus oxide (VPO)
[9,10]
cosmetics and polymer building blocks.
e.g., γ-butyrolactone
catalysts are efficient for n-butane oxidation into maleic
[18]
(
GBL) could be used as an intermediate in the manufacture of
anhydride in industry. For homogenous catalysis, oxovana-
[9]
pyrrolidone derivatives, or as a solvent for polymers. Aliphatic
polyesters prepared by ring-opening polymerization of δ-
[a] C. Xiao, Z. Du, Prof. C. Liang
State Key Laboratory of Fine Chemicals
Dalian University of Technology
Dalian, 116024 (P. R. China)
E-mail: duzhongtian@dlut.edu.cn
changhai@dlut.edu.cn
[
b] C. Xiao, Z. Du, S. Li, Y. Zhao, Prof. C. Liang
School of Chemical Engineering
Dalian University of Technology
Panjin 124221 (P. R. China)
Supporting information for this article is available on the WWW under
https://doi.org/10.1002/cctc.202000288
Scheme 1. Several methods for the preparation of γ-butyrolactone (GBL).
ChemCatChem 2020, 12, 1–7
1
© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
��
These are not the final page numbers!

Communications
doi.org/10.1002/cctc.202000288
ChemCatChem
dium could also easily form complexes with heteroatom (e.g. O
or N), and it is a typical strategy to regulate the catalytic
performances of vanadium complexes by using different
catalyst was prepared at 400°C, and cyclohexanone was
determined as the main product (Table 1, entry 2). Up to 89%
of cyclohexanol was smoothly oxidized when VÀ NÀ C-500 was
employed (Table 1, entry 3). Unexpectedly, oxidative CÀ C bond
cleavage occurred. Only 23% selectivity of cyclohexanone was
obtained, and up to 60% of lactones, including 40% of γ-
butyrolactone and 20% of δ-valerolactone, were detected
(Table 1, entry 3). Other products are mainly 2-cyclohexen-1-
one, formic acid, cyclohexyl formate and carbon dioxide. Few
reports have described the formation of lactones as main
products via aerobic oxidation of cyclohexanol previously. Such
a transformation would be rather attractive, as the selective
oxidation could be tuned at lactones, rather than the common
dicarboxylic acids. When VÀ NÀ C-600 was used as a catalyst,
95% of cyclohexanol could be oxidized, however, the total
selectivity of lactones is only about 23%, and up to 73%
selectivity of cyclohexanone was observed (Table 1, entry 4).
Therefore, the thermal treatment temperature of VÀ NÀ C
materials has great effects on the corresponding catalytic
activities. Moreover, melamine and NH VO was pyrolysis/
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
[19–21]
organic ligands.
In previous reports, we also described
unique activities of homogeneous vanadium catalysts for
alcohol oxidation and oxidative CÀ C bond cleavage under mild
[22–25]
reaction conditions.
Recently, atomically dispersed metal-
NÀ C materials have emerged as promising materials for various
applications of interest such as energy storage, separation and
[26–31]
catalysis.
Research in this field has demonstrated that
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
nitrogen doping is an effective way to tailor the properties of
carbon and the electron density at the metal centers, which is
analogous to the function of a ligand in homogeneous catalysis.
We wonder the opportunities to modify the electronic environ-
ments and chemical structures of vanadium nanocatalysts, and
tune their catalytic performances by introduction of nitrogen
atoms. Herein we report VÀ NÀ C composites for catalytic
oxidative CÀ C bond cleavage of cyclohexanol with molecular
oxygen into lactones, and the surface structure of VÀ NÀ C
catalysts prepared at different pyrolysis temperature varied
greatly as well as the catalytic activity.
4
3
calcined by a similar method at 500°C, and the received
The fabrication process of the VÀ NÀ C catalysts is summar-
ized as follows (Schematic illustration see Supporting Informa-
tion, Scheme S1): Firstly, melamine was dispersed in hot water,
materials (NH VO -500 and melamine-500) were employed for
4
3
catalytic oxidation. In contrast, low conversion of cyclohexanol
was obtained respectively (Table 1, entries 5 and 6). Further,
commercial V O , NH VO , and melamine was also used
and then NH VO3 was added slowly under vigorous stirring
4
2
5
4
3
(
molar ratio of melamine/NH VO =1:3). The solution was
respectively in place of VÀ NÀ C-500 catalyst, however, the
conversion of cyclohexanol was rather low under the same
reaction conditions, and no lactones were observed (Table 1,
entry 7). In a previous report, Tong and coworkers fabricated
VÀ NC->C composites via directly annealing the mixture of
NH VO and melamine as anode materials for lithium ion
4
3
cooled at 0–5°C, and the deposited blend was dried under
vacuum at 100°C. After grinding into a powder (VÀ NÀ C
precursor), it was subjected to thermal treatment under a flow
of nitrogen atmosphere at specifically regulated temperatures
to afford the VÀ NC->C catalysts. The materials calcined at
different temperatures were denoted as VÀ NÀ C-x (x: thermal
treatment temperature).
Initially, catalytic oxidation of cyclohexanol with molecular
oxygen was carried out in acetonitrile (Table 1). As a secondary
alcohol, cyclohexanol is generally resistant to oxidation with
molecular oxygen. As expected, no significant oxidation took
place without a catalyst (Table 1, entry 1). The materials calcined
at different temperatures were used as the catalyst respectively.
Only 2% conversion of cyclohexanol was observed when the
4
3
[28]
batteries. However, when VÀ NÀ C-mix-500 was prepared via a
similar method and used for catalytic oxidation, low conversion
of cyclohexanol was observed (Table 1, entry 8). All these
experimental results suggest that the sample prepared at
500°C exhibited unique catalytic activity for oxidative CÀ C
bond fission of cyclohexanol, compared with VÀ NÀ C-400,
VÀ NÀ C-600, and the starting materials. The structure of the
VÀ NÀ C-500 catalyst will be discussed in the following para-
graphs.
[a]
Table 1. Oxidation of cyclohexanol with dioxygen using different catalysts.
[
b]
Entry
Catalyst
Conversion
%]
Selectivity of main products [%]
[
1
2
3
4
none
<1
2
89
95
2
2
3
2
–
>99
–
–
–
–
VÀ NÀ C-400
VÀ NÀ C-500
VÀ NÀ C-600
Melamine-500
NH VO -500
23
73
>99
>99
>99
>99
40
15
–
–
–
20
8
–
–
–
–
[c]
5
[
c]
6
7
8
4
3
V
2
O
5
[
d]
VÀ NÀ C-mix-500
–
[
a] Reaction conditions: 5 mmol cyclohexanol, 5 wt% catalyst, 3 mL MeCN, 0.5 MPa O
2
, 120°C, 8 h. [b] Other products, including 2-cyclohexen-1-one,
cyclohexyl formate, formic acid and carbon dioxide, were detected. [c] Melamine or NH VO
4
3
was pyrolysed/calcined at 500°C. [d] NH
4 3
VO and melamine was
mixed mechanically before thermal treatment (molar ratio of melamine/NH
4
VO
3
=1:3). For more details, see SI experimental section.
ChemCatChem 2020, 12, 1–7
www.chemcatchem.org
2
© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
��
These are not the final page numbers!

Communications
doi.org/10.1002/cctc.202000288
ChemCatChem
We further studied the reaction progress of cyclohexanol
calcined temperature was 500 and 600°C, the XRD patterns of
received materials were quite different from that of VÀ NÀ C-400.
The peaks around 26° were still broad and weak, which
suggests the as-obtained materials possess amorphous carbon
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
oxidation over VÀ NC->C-500 catalyst (Figure 1). About 78% of
cyclohexanol could smoothly be converted with 92% selectivity
of cyclohexanone within 4 h, and only a few of lactones were
detected. When the reaction time was prolonged to 6 h, the
selectivity of lactones increased substantially, with the signifi-
cant decrease of cyclohexanone. This observation suggests that
cyclohexanone was probably an important intermediate during
the oxidation of cyclohexanol into lactones. Within 8 h, 89%
conversion of cyclohexanol could be obtained with 60% total
selectivity of lactones, and the selectivity of cyclohexanone was
also decreased to 23%. However, the conversion of cyclo-
hexanol only increased slightly to about 90% after 10 h. It is
notable that 1~2% of 2-cyclohexen-1-one always existed in the
oxidation products from 4–10 h, which is probably related with
the reaction pathway.
Now one of key issues is the structure and surface property
of the VÀ NÀ C catalysts that related with catalytic oxidation. The
catalysts calcined at different temperature (400, 500 and 600°C)
were analysed by X-ray diffractometer (XRD), as showed in
Figure 2. Only a broad peak with low intensity located around
6° was observed from the XRD pattern of VÀ NÀ -400. When the
[32,33]
with a low degree of graphitization.
V O (PDF#76-0146)
2 3
[34]
was detected from the pattern of VÀ NÀ C-500,
which
indicated that low-valence vanadium oxide appeared via the
reduction reaction of NH VO . Weak peaks at 43.6 ° and 63.4°
4
3
were also detected, which could be indexed to vanadium
[
34,35]
nitride (VN, PDF#35-0768).
However, the peaks of VN in our
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
[
34–36]
work were much weaker than those in previous reports,
demonstrating that part of vanadium oxides were transformed
into VN with a low crystallinity. We further performed TG
analysis to study the thermal treatment process of VÀ NÀ C-
precursor (Supporting Information, Figure S3). The weight loss
from 100 to 250°C could be attributed to the absorbed water in
surface and crystal water of the precursor. With the increase of
temperature, the decomposition of NH VO into V O led to
4
3
2
5
significant weight loss from 250~350°C, as the melamine is
stable before 354°C. The decomposition of melamine as well as
reduction of V O took place between 350~600°C, which could
2
5
2
lead to the formation of VN and V O . When the temperature
x y
was further raised, only slight loss was observed. XRD and TG
results clearly indicate that the precursor could be transformed
into different VÀ NÀ C materials under different thermal treat-
ment temperature. These changing structures should be related
with the different catalytic activities for oxidative CÀ C bond
cleavage.
The XPS studies were further performed to obtain more
information about the surface composition of VÀ NÀ C-400,
VÀ NÀ C-500 and VÀ NÀ C-600 (Figures 3, 4 and Figure S1). All the
three materials have C, N, V, and O elements as depicted in the
XPS survey spectra (Supporting Information, Figure S1, a). For
the samples VÀ NÀ C-500 and VÀ NÀ C-600, the high-resolution of
C 1s spectrum shows three fitting peaks (284.3, 286.0 and
2
88.6 eV, Figure S1, b in Supporting Information). The peak
Figure 1. Reaction progress of cyclohexanol oxidation over the VÀ NÀ C-500
catalyst. Reaction conditions: 5 mmol cyclohexanol, 5 wt% catalyst, 3 mL
MeCN, 0.5 MPa O
2
, 120°C.
Figure 3. XPS spectra of O 1s and V 2p for the VÀ NÀ C-400, VÀ NÀ C-500 and
VÀ NÀ C-600 catalysts.
Figure 2. XRD patterns of VÀ NÀ C catalysts calcined at different temperature.
ChemCatChem 2020, 12, 1–7
www.chemcatchem.org
3
© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
��
These are not the final page numbers!

Communications
doi.org/10.1002/cctc.202000288
ChemCatChem
around 284.3 eV could be ascribed to the doubly coordinated
carbons, and the other two peaks of 286.0 and 288.6 eV can be
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
[37,38]
assigned to CÀ N, and C=O bonds respectively.
In contrast,
for the sample prepared at 400°C, the C 1s component of the
XPS spectrum could only be divided into two main regions
(284.4 and 287.9 eV). These results display the different existing
form of carbon on the surface after pyrolysis at different
temperature.
V 2p and O 1s components of the XPS spectra were usually
put together for analysis because their binding energy is very
close (Figure 3). The peaks from left to right correspond to O 1s,
V 2p1/2, and V 2p3/2. The O 1s spectrum of VÀ NÀ C-400 and
VÀ NÀ C-500 was divided into two main peaks centered at 529.9
and 531.0 eV, respectively. The peak at 529.9 eV suggests the
existence of VÀ O component of vanadium oxides on the
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
Figure 4. XPS spectra of N 1s (left) and types of nitrogen functionalities
(right) for the VÀ NÀ C-400, VÀ NÀ C-500 and VÀ NÀ C-600 catalysts.
[39,40]
material surface.
These results agree with XRD patterns
38% as graphitic nitrogen, and 42% as vanadium nitride (VN)
for the sample of VÀ NÀ C-500, while 48% of the nitrogen was
found as pyrrolic nitrogen, 35% as graphitic nitrogen, and 17%
as vanadium nitride (VN) for that of VÀ NÀ C-600. In contrast,
only two peaks at 398.4 and 399.4 eV were found for sample
VÀ NÀ C-400, which were ascribed to pyridinic-N (34%) and
mentioned above. Another peak at 531.8 eV in the VÀ NÀ C-600
sample could be attributed to the existence -OH groups formed
[40]
in the process of heat treatment on the surface.
These
differences are reasonable, and consistent with the above XRD
and C1s XPS analysis. As expected, the high-resolution V 2p3/2
XPS spectra also exhibit different oxidation states of vanadium
[27,38,43,44]
pyrrolic-N (66%) respectively.
Though the role of nitro-
(
Figure 3). A peak at 516.6 eV was dominant for the VÀ NÀ C-400
gen species during catalytic oxidation is still unclear, the
percentage of VN in the VÀ NÀ C-500 sample is highest among
these materials, which meets the unique catalytic activity of
VÀ NÀ C-500.
4
+
sample, which could be ascribed to V
vanadium oxides.
in the form of
[36]
In contrast, the V2p3/2 spectra of the
VÀ NÀ C-500 can obviously be divided into three peaks. The
3
+
peaks at 514.3 eV could be attributed to V species, which
might be related with VN and V O , according to XRD and O 1s
Raman spectroscopy is widely used to investigate the
graphitic nature and concentration of defects in metal-NÀ C
2
3
[27]
XPS analysis. Nevertheless, the bonding energy difference of
vanadium species is very close, it is difficult to exactly
materials.
We further performed Raman spectroscopy to
detect more information about the VÀ NÀ C-500 sample (Sup-
[39]
distinguish the presence of vanadium oxynitride. Moreover,
porting Information, Figure S4). The Raman peaks in the range
4
+
5+
À 1
V
and V species was also observed. The peaks at 516.2 eV
of 100–1100 cm correspond to the characteristic peaks of
4
+
were recognized as V species, while the peaks at 517.4 eV
vanadium oxides and VN, and the characteristic peaks at 140
5
+
À 1
were ascribed to V species. Based on the analysis of the XPS
spectra, we believe that VÀ NÀ C-500 and VÀ NÀ C-600 are mainly
composed of vanadium oxide-nitride composites, together with
amorphous carbon on the surface. Vanadium oxides and nitride
with different oxidation states coexisted on the surface, and the
distribution of vanadium with different oxidation states was
shown in Figure S2 (Supporting Information). Approximately
and 281 cm are ascribed to acoustic band of VN, while that at
À 1
[34,41]
691 cm is related with optical band of VN.
However, two
À 1
bands centered at ca.1350 and 1560 cm , which could be
assigned to the disordered/defected carbon (D band) and
2
[27,38,45]
graphitic sp carbon (G band) respectively,
are rather
weak. These results demonstrate that the amorphous carbons
predominate in the sample VÀ NÀ C-500 with a low degree of
graphitization. VN and vanadium oxides coexist with such
amorphous carbon composites with a low crystallinity, based
on all the analysis depicted above.
3
+
4+
5+
1
0% of V , 29% of V , and 61% of V were found in the
+
3
4+
sample of VÀ NÀ C-500, and 13% of V , 19% of V and 67% of
were detected for the sample of VÀ NÀ C-600. Meanwhile,
nearly 100% V was determined for VÀ NÀ C-400. As VÀ NÀ C-
00 (V ), NH VO -500 (V ), and V O (V ) showed rather low
5
+
V
4
+
The morphologies and microstructures of VÀ NÀ C compo-
sites were further examined. The scanning electron microscopy
(SEM) images show that sheet-like morphology dominates,
though the sample of VÀ NÀ C-500 does not have a specific
shape (Supporting Information, Figure S5). The selected-area
analysis of VÀ NÀ C-500 by the transmission electron microscopy
(TEM) also indicates the presence of nano-sheets (Figure 5).
Moreover, the corresponding EDS elemental mapping was also
analysed. The green, orange, red, and yellow images stand for
the distribution of V, N, C and O, respectively. The elements V,
N, C and O were coexistent and homogeneously distributed
throughout the whole VÀ NÀ C-500 composites. We believe that
vanadium species (V O and VN) are well dispersed on the
4
+
5+
5+
4
4
3
2
5
3
+
catalytic activity (Table 1, entries 2, 6 and 7), the presence of V
species was most likely related with the enhanced catalytic
activity for CÀ C bond cleavage, and the redox cycles of
vanadium among different valence states are predictable during
catalytic oxidation.
Additionally, the existing form of nitrogen was also quite
different on the surface (Figure 4). For the N 1s line of VÀ NÀ C-
5
00 and VÀ NÀ C-600, they were fitted with three peaks centered
at 397.0, 399.2 and 401.8 eV by means of XPS peak differ-
entiation-imitating analysis, corresponding to the characteristic
of VN, pyrrolic, and graphitic nitrogen respectively.
[27,42]
Approx-
y
x
imately 20% of the nitrogen was bonded as pyrrolic nitrogen,
amorphous carbon successfully.
ChemCatChem 2020, 12, 1–7
www.chemcatchem.org
4
© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
��
These are not the final page numbers!

Communications
doi.org/10.1002/cctc.202000288
ChemCatChem
oxidation of cyclohexanone might afford 2-hydroxy-1-
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
[14,15,46]
cyclohexanone.
Vanadium-catalyzed CÀ C bond cleavage
of 2-hydroxy-1-cyclohexanone into dicarboxylic acid with mo-
lecular oxygen was known in previous reports.
[47,48]
It is
reasonable that selective oxidation of 2-hydroxy-1-cyclohexa-
none into lactones via CÀ C bond cleavage occurred over
VÀ NÀ C catalysts, which could afford δ-valerolactone. Meanwhile
2
-cyclohexen-1-one was also produced via dehydration, and
then oxidized into γ-butyrolactone. These lactones are resistant
to further oxidation.
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
Finally, the reusability of the VÀ NÀ C composites was
investigated for catalytic oxidation of cyclohexanol with molec-
ular oxygen. However, direct reuse of the VÀ NÀ C-500 catalyst
exhibited much lower catalytic activity under the same reaction
conditions. Only 17% conversion of cyclohexanol was obtained
within 8 h, and cyclohexanone was the only product. The
catalyst after use became dark green, while the fresh is black.
Only a broad and weak peak around 25°C could be observed
from the XRD pattern of the VÀ NÀ C-500 after use (Supporting
Information, Figure S6), which is quite different from that before
use. There are several possible aspects that caused the activity
loss for VÀ NÀ C materials in liquid phase oxidation. When
molecular oxygen is used as an oxidant, water was gradually
released as a byproduct. We previously observed the deactiva-
Figure 5. The TEM image and element mapping of V, N, C and O of the as-
prepared VÀ NÀ C-500 catalyst.
Besides surface and structural property of catalysts, another
important issue is the formation reaction pathway of lactones
from cyclohexanol. Several control experiments were carried
out over the VÀ NÀ C-500 catalyst (Supporting Information,
Table S4). When the reaction of cyclohexanol was performed
under a nitrogen atmosphere, only 4% conversion of cyclo-
hexanol was observed with 8 h, and no lactones were detected.
Thus, the dehydrogenation reaction under an inert environment
is not dominant, and molecular oxygen is indispensable.
Catalytic oxidation of cyclohexanol was also tested in the
presence of 5 mol% free radical inhibitors including 2,6-di-tert-
butyl-p-cresol (BHT) and 2,2,6,6-tetramethyl-1-piperidinyloxy
[
22,49]
tion of some vanadium catalytic systems by water.
Furthermore, formic acid was also formed due to oxidative CÀ C
bond cleavage (Supporting Information, Figure S7), and such an
acidic environment would cause destruction of vanadium
[50]
(TEMPO). Unexpectedly, 90% and 94% conversion of cyclo-
oxides,
and neutralize basic nitrogen-containing species,
hexanol could still be obtained with 48% and 25% selectivity of
total lactones within 8 h respectively. These results suggest that
free radical chain reactions did not predominate during
oxidation of cyclohexanol into lactones. As described above
which could result in a significant change of vanadium active
sites and the corresponding catalytic activity.
In summary, vanadium oxide–nitride composites in the form
of nano-sheets were fabricated via a facile thermal treatment
process. Cyclohexanol could be selectively oxidized with
molecular oxygen into valuable lactones including δ-valerolac-
tone and γ-butyrolactone, rather than dicarboxylic acids. The
thermal treatment temperature could alter the surface and
structural property of these VÀ NÀ C composites significantly,
and affect the catalytic activities consequently. Over the
VÀ NÀ C-500 catalyst, 89% conversion of cyclohexanol could
easily obtained with a 60% total selectivity of lactones at 120°C
within 8 h. Cyclohexanone and 2-cyclohexen-1-one were veri-
(Figure 1), the reaction progress profile showed that cyclo-
hexanone was the major product within 4 h, and decreased
significantly when the reaction time was prolonged. As
expected, when cyclohexanone was directly subjected to
oxidation (Supporting Information, Scheme S2), it was smoothly
converted into γ-butyrolactone and δ-valerolactone with 99%
conversion in 8 h, and the total selectivity of lactones is up to
7
9%. Thus, cyclohexanone was undoubtedly one of key
intermediates during the formation of lactones. Moreover, 2-
cyclohexen-1-one was always detected in the oxidation prod-
ucts, though the concentration was always rather low. We
subsequently performed the direct oxidation of 2-cyclohexen-1-
one under the same reaction conditions above. To our delight,
3
+
fied as two key intermediates. V
species in the form of
vanadium nitride and vanadium (III) oxide were well dispersed
on amorphous carbon with a low degree of graphitization,
which was most likely related with the enhanced catalytic
activity for oxidative CÀ C bond cleavage. These results will
provide researchers with new ideas for catalytic oxidative CÀ C
bond cleavage, and would be also useful in the other fields
such as breakdown of lignocellulose and degradation of
polymers.
7
6% selectivity of γ-butyrolactone was observed with 19%
conversion of 2-cyclohexen-1-one (Supporting Information,
Scheme S2). Further we carried out catalytic oxidation of γ-
butyrolactone and δ-valerolactone under the same reaction
conditions, and no further oxidation was observed, which
indicated that γ-butyrolactone and δ-valerolactone could
remain stable under the oxidative reaction conditions.
Based on the above results, we reasoned a proposed Acknowledgements
reaction pathway from cyclohexanol to lactones over VÀ NÀ C
catalysts (Supporting Information, Scheme S3). Firstly, cyclo-
hexanol was oxidized into cyclohexanone, and then further
This work was supported by the National Natural Science
Foundation of China (21473184), the Fundamental Research
ChemCatChem 2020, 12, 1–7
www.chemcatchem.org
5
© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
��
These are not the final page numbers!

Communications
doi.org/10.1002/cctc.202000288
ChemCatChem
Funds for the Central Universities (DUT15RC(3)094), and the
Natural Science Foundation of Liaoning Province (2019-MS-047).
[25] Z. Du, J. Ma, F. Wang, J. Liu, J. Xu, Green Chem. 2011, 13, 554–557.
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
[
26] D. Zhao, K. Sun, W.-C. Cheong, L. Zheng, C. Zhang, S. Liu, X. Cao, K. Wu,
Y. Pan, Z. Zhuang, B. Hu, D. Wang, Q. Peng, C. Chen, Y. Li, Angew. Chem.
Int. Ed. In press, DOI: 10.1002/anie.201908760.
[
27] L. He, F. Weniger, H. Neumann, M. Beller, Angew. Chem. Int. Ed. 2016, 55,
12582–12594; Angew. Chem. 2016, 128, 12770–12783.
Conflict of Interest
[28] B. Long, M.-S. Balogun, L. Luo, Y. Luo, W. Qiu, S. Song, L. Zhang, Y. Tong,
Small 2017, 13, 1702081.
[29] M. Li, F. Xu, H. Li, Y. Wang, Catal. Sci. Technol. 2016, 6, 3670–3693.
The authors declare no conflict of interest.
[
30] X.-H. Li, M. Antonietti, Chem. Soc. Rev. 2013, 42, 6593–6604.
[31] Y. Pan, Y. Chen, K. Wu, Z. Chen, S. Liu, X. Cao, W.-C. Cheong, T. Meng, J.
Luo, L. Zheng, C. Liu, D. Wang, Q. Peng, J. Li, C. Chen, Nat. Commun.
Keywords: Lactones · Oxidation · Heterogeneous catalysis ·
Vanadium · CÀ C bond cleavage
2
019, 10. 4290.
32] J. Liu, F. Li, W. Liu, X. Li, Inorg. Chem. Front. 2019, 6, 164–171.
[33] J. Peng, N. Chen, R. He, Z. Wang, S. Dai, X. Jin, Angew. Chem. Int. Ed.
017, 56, 1751–1755; Angew. Chem. 2017, 129, 1777–1781.
34] M. Wu, H. Guo, Y.-n. Lin, K. Wu, T. Ma, A. Hagfeldt, J. Phys. Chem. C 2014,
18, 12625–12631.
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
[
2
[
[
1] V. Escande, C. H. Lam, P. Coish, P. T. Anastas, Angew. Chem. Int. Ed. 2017,
1
56, 9561–9565; Angew. Chem. 2017, 129, 9689–9693.
[35] F. Cheng, C. He, D. Shu, H. Chen, J. Zhang, S. Tang, D. E. Finlow, Mater.
[2] H. Luo, L. Wang, G. Li, S. Shang, Y. Lv, J. Niu, S. Gao, ACS Sustainable
Chem. Eng. 2018, 6, 14188–14196.
Chem. Phys. 2011, 131, 268–273.
36] A. M. Glushenkov, D. Hulicova-Jurcakova, D. Llewellyn, G. Q. Lu, Y. Chen,
[
[
3] M. Wang, J. Lu, J. Ma, Z. Zhang, F. Wang, Angew. Chem. Int. Ed. 2015, 54,
4061–14065; Angew. Chem. 2015, 127, 14267–14271.
[4] S. K. Hanson, R. Wu, L. A. P. Silks, Angew. Chem. Int. Ed. 2012, 51, 3410–
413; Angew. Chem. 2012, 124, 3466–3469.
5] L. Shuai, J. Sitison, S. Sadula, J. Ding, M. C. Thies, B. Saha, ACS Catal.
018, 8, 6507–6512.
[6] E. Amadio, R. Di Lorenzo, C. Zonta, G. Licini, Coord. Chem. Rev. 2015,
01, 147–162.
Chem. Mater. 2010, 22, 914–921.
[37] Y. Wu, F. Ran, J. Power Sources 2017, 344, 1–10.
1
[
[
[
[
[
[
[
38] W. Zhang, P. Oulego, T. K. Slot, G. Rothenberg, N. R. Shiju, ChemCatChem
3
2
019, 11, 3381–3387.
[
39] E. F. de Souza, C. A. Chagas, T. C. Ramalho, V. T. da Silva, D. L. M. Aguiar,
R. San Gil, R. B. de Alencastro, J. Phys. Chem. C 2013, 117, 25659–25668.
40] Y. Yang, L. Zhao, K. Shen, Y. Liu, X. Zhao, Y. Wu, Y. Wang, F. Ran, J. Power
Sources 2016, 333, 61–71.
41] C. M. Ghimbeu, E. Raymundo-Pinero, P. Fioux, F. Beguin, C. Vix-Guterl, J.
Mater. Chem. 2011, 21, 13268–13275.
2
3
[
7] X. Huang, X. Li, M. Zou, S. Song, C. Tang, Y. Yuan, N. Jiao, J. Am. Chem.
Soc. 2014, 136, 14858–14865.
[8] A. Rahimi, A. Azarpira, H. Kim, J. Ralph, S. S. Stahl, J. Am. Chem. Soc.
013, 135, 6415–6418.
42] T. Lin, I. W. Chen, F. Liu, C. Yang, H. Bi, F. Xu, F. Huang, Science 2015,
2
350, 1508–1513.
[
9] W. Schwarz, J. Schossig, R. Rossbacher, H. Höke, Butyrolactone in
Ullmann’s Encyclopedia of Industrial Chemistry (7th Edition), Wiley-VCH,
Weinheim, 2011.
10] K. Makiguchi, T. Satoh, T. Kakuchi, Macromolecules 2011, 44, 1999–2005.
11] A. Corma, L. T. Nemeth, M. Renz, S. Valencia, Nature 2001, 412, 423–425.
12] T. Mitsudome, A. Noujima, T. Mizugaki, K. Jitsukawa, K. Kaneda, Green
Chem. 2009, 11, 793–797.
43] R. Arrigo, M. Haevecker, R. Schloegl, D. S. Su, Chem. Commun. 2008,
4891–4893.
44] X. Wang, C.-G. Liu, D. Neff, P. F. Fulvio, R. T. Mayes, A. Zhamu, Q. Fang,
G. Chen, H. M. Meyer, B. Z. Jang, S. Dai, J. Mater. Chem. A 2013, 1, 7920–
[
[
[
7926.
[45] L. Qie, W.-M. Chen, Z.-H. Wang, Q.-G. Shao, X. Li, L.-X. Yuan, X.-L. Hu, W.-
X. Zhang, Y.-H. Huang, Adv. Mater. 2012, 24, 2047–2050.
46] F. Cavani, L. Ferroni, A. Frattini, C. Lucarelli, A. Mazzini, K. Raabova, S.
[
13] M. Selva, M. Gottardo, A. Perosa, ACS Sustainable Chem. Eng. 2013, 1,
[
180–189.
Alini, P. Accorinti, P. Babini, Appl. Catal. A 2011, 391, 118–124.
[
14] S. Van de Vyver, Y. Roman-Leshkov, Catal. Sci. Technol. 2013, 3, 1465–
[47] M. Vennat, P. Herson, J. M. Bregeault, G. B. Shul’pin, Eur. J. Inorg. Chem.
003, 908–917.
48] L. El Aakel, F. Launay, A. Atlamsani, J. M. Bregeault, Chem. Commun.
001, 2218–2219.
[49] Z. Du, J. Ma, H. Ma, J. Gao, J. Xu, Green Chem. 2010, 12, 590–592.
1479.
2
[15] J. C. J. Bart, S. Cavallaro, Ind. Eng. Chem. Res. 2015, 54, 1–46.
[16] M. Kirihara, Coord. Chem. Rev. 2011, 255, 2281–2302.
[17] R. R. Langeslay, D. M. Kaphan, C. L. Marshall, P. C. Stair, A. P. Sattelberg-
er, M. Delferro, Chem. Rev. 2019, 119, 2128–2191.
[
2
[
50] D. Rehder, Bioinorganic Vanadium Chemistry. John Wiley
Chichester, 2008, 13–26.
& Sons,
[18] F. Cavani, J. H. Teles, ChemSusChem 2009, 2, 508–534.
[19] A. Butler, M. J. Clague, G. E. Meister, Chem. Rev. 1994, 94, 625–638.
[20] M. Sutradhar, L. M. D. R. S. Martins, M. F. C. G. da Silva, A. J. L. Pombeiro,
Coord. Chem. Rev. 2015, 301, 200–239.
[
[
[
21] S. K. Hanson, R. Wu, L. A. P. Silks, Org. Lett. 2011, 13, 1908–1911.
22] Z. Du, J. Liu, T. Lu, Y. Ma, J. Xu, Sci. China Chem. 2015, 58, 114–122.
23] Y. Ma, Z. Du, J. Liu, F. Xia, J. Xu, Green Chem. 2015, 17, 4968–4973.
Manuscript received: February 17, 2020
Revised manuscript received: March 28, 2020
Version of record online: ■■■, ■■■■
[24] J. Liu, Z. Du, Y. Yang, T. Lu, F. Lu, J. Xu, ChemSusChem 2012, 5, 2151–
2154.
ChemCatChem 2020, 12, 1–7
www.chemcatchem.org
6
© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
��
These are not the final page numbers!

1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
COMMUNICATIONS
C. Xiao, Z. Du*, S. Li, Y. Zhao, Prof. C.
Liang*
1 – 7
Vanadium Oxide-Nitride Compo-
sites for Catalytic Oxidative CÀ C
Bond Cleavage of Cyclohexanol
into Lactones with Dioxygen
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
VÀ NÀ C catalysts were prepared via a
thermal treatment process for
catalytic oxidative CÀ C bond cleavage
with molecular oxygen. Cyclohexanol
was selectively oxidized with
rather than common dicarboxylic
acids. Cyclohexanone and 2-cyclohex-
en-1-one were verified as two key in-
termediates, and vanadium nitride
and vanadium (III) oxide were
detected on the surface of VÀ NÀ C-
500.
dioxygen into lactones including δ-va-
lerolactone and γ-butyrolactone,