Copper Tetrasulfophthalocyanine Intercalated Hydrotalcite as an Efficient Bifunctional Catalyst for the Baeyer–Villiger Oxidation

Article abstract of DOI:10.1007/s10562-016-1823-5

Abstract: A heterogeneous bifunctional hybrid catalyst originated from copper tetrasulfophthalocyanine (CuPcTs) and hydrotalcite for Baeyer–Villiger (B-V) oxidation has been prepared and characterized. XRD, FTIR, DR UV-Vis and SEM characterization indicate that CuPcTs molecule has been successfully intercalated into the layer of ZnAl hydrotalcite. And the synthesized hybrid exhibited excellent catalytic activity in the B-V oxidation for various ketones under mild conditions. Its bifunctional role in the reaction through O₂/benzaldehyde has been discussed and verified by controlled experiments. The study indicates that the designed catalyst not only catalyzes the oxidation of benzaldehyde to perbenzoic acid, but also accelerates the transformation of ketone to lactone or ester. Graphical Abstract: [Figure not available: see fulltext.]

Full text of DOI:10.1007/s10562-016-1823-5

Catal Lett
DOI 10.1007/s10562-016-1823-5
Copper Tetrasulfophthalocyanine Intercalated Hydrotalcite as an
Efficient Bifunctional Catalyst for the Baeyer–Villiger Oxidation
Weiyou Zhou1 · Yong Chen1 · Junfeng Qian1 · Fu’an Sun1 · Mingyang He1 ·
Qun Chen1
Received: 27 May 2016 / Accepted: 20 July 2016
© Springer Science+Business Media New York 2016
Keywords Hydrotalcite-like compounds ·
Copper phthalocyanine · Baeyer–Villiger oxidation ·
Bifunctional catalyst
Abstract A heterogeneous bifunctional hybrid catalyst
originated from copper tetrasulfophthalocyanine (CuPcTs)
and hydrotalcite for Baeyer–Villiger (B-V) oxidation has
been prepared and characterized. XRD, FTIR, DR UV-Vis
and SEM characterization indicate that CuPcTs molecule
has been successfully intercalated into the layer of ZnAl
hydrotalcite. And the synthesized hybrid exhibited excellent
catalytic activity in the B-V oxidation for various ketones
under mild conditions. Its bifunctional role in the reaction
through O2/benzaldehyde has been discussed and verified
by controlled experiments. The study indicates that the
designed catalyst not only catalyzes the oxidation of benzal-
dehyde to perbenzoic acid, but also accelerates the transfor-
mation of ketone to lactone or ester.
1 Introduction
The Baeyer–Villiger (B-V) oxidation is an important reac-
tion for directly transforming a ketone to a lactone or ester,
and has been widely applied in organic synthesis and fine
chemical industries [1–3]. Peroxides, such as persulfuric
acid [4], perbenzoic acid [5, 6], tert-butylhydroperoxide
[7], m-chloroperbenzoic acid (m-CPBA) and hydrogen per-
oxide (H2O2) [8–11] are commonly used in the reaction.
However, these oxidants not only require expensive protec-
tion, some of them but also cause a lot of waste material, the
O2/aldehyde oxidation system will be quite attractive from
an industrial viewpoint.
Graphical Abstract
Actually, varied materials have been introduced to cata-
lyze the B-V oxidation through O2/aldehyde, including
metallo complexes [12], active carbon [13], transition metal
ions or their oxides [14–17], metals supported on various
supports [18–20] and hydrotalcites [21, 22], etc. According
to the generally accepted reaction scheme for the oxidation
system consists of two reaction steps, namely peracid for-
mation from aldehyde and O2 and the oxidation of the reac-
tant by the peracid [23].
However, most of the reported catalysts could only cata-
lyze one of the two steps. Developing a bifunctional catalyst
on the basis of the reaction mechanism, which can catalyze
both of the reaction steps, should be very attractive. Kaneda
et al. [24] had introduced a transition metal like Fe, which
has catalytic activity in the oxidation of aldehyde, into the
hydrotalcite structure, and found that the catalytic activities
ꢀ Mingyang He
hemy_cczu@126.com
1
Jiangsu Key Laboratory of Advanced Catalytic Materials and
Technology, Changzhou University, Changzhou
213164, China
1 3

2
W. Zhou et al.
of the new catalysts were substantially improved in the B-V
oxidation.
CuPcTs into ZnAl hydrotalcite was 22.7% by weight; the
Zn/Al atomic ratio was estimated to 2.0, which is consistent
with the expected composition for the host structure.
On the other hand, metallophthalocyanine, as a biomi-
metic catalyst for P450, has received considerable atten-
tion and exhibited excellent performance in the oxidation
of varied substrates using oxygen as the oxidant [25–28].
Therefore, we speculated that the metallophthalocyanine
molecule may also exhibit catalytic activity in the first step
of B-V oxidation, namely the transformation of benzalde-
hyde to perbenzoic acid.
On the basis of above analysis, we envisioned that the
hybrid formed by intercalating metallophthalocyanine into
hydrotalcite (LDH) may accelerate both of the steps in the
B-V oxidation by O2/aldehyde, since hydrotalcite has been
generally proved to be an effective catalyst for the second
step [22]. In addition, the intercalated materials would also
afford a heterogeneous catalyst for metallophthalocyanine
and increase its durability in reactions [18], because the
deactivation of active sites is always caused by oxidative
decomposition and aggregation of metallo complex by π–π
interaction in homogeneous system.
In our previous research, we have developed a cobalt
porphyrin intercalated hydrotalcite hybrid for the reaction,
and excellent catalytic activity in the B-V oxidation of var-
ied ketones was observed [29]. In the present study, Copper
tetrasulfophthalocyanine anion (CuPcTs), which is probably
more accessible than metalloporphyrins from a preparation
point of view, intercalated ZnAl hydrotalcite has been pre-
pared as a bifunctional catalyst for the aerobic B-V oxida-
tion under milder conditions.
2.2 Characterization of Catalysts
The compositions of samples were analyzed by ICP using a
Varian Vista-AX device. The XRD patterns were recorded
on a Rigaku D/max 2500 PC X-ray generator with Cu-Kα
(1.5402 Å) radiation at 10 min−1. Basal spacing distances
were determined from the position of the d(003) reflection.
FTIR spectra of samples were recorded using KBr disks on
a Nicolet PROTÉGÉ 460 FTIR spectrometer. For the SEM
study of the LDHs, a JEOL JSM-6360LA scanning electron
microscope was used. Diffuse reflectance ultraviolet visible
spectroscopy (DR UV-Vis) was analyzed on a Perkin-Elmer
Instruments Lambda 35.
2.3 Catalytic B-V Oxidation
The catalytic oxidation of ketone was carried out in a round-
bottom flask of 25 mL volume equipped with magnetic stir-
rer. In the typical experiment, the flask was charged with
substrate (2 mmol), CuPcTs-Zn2Al-LDH (8.0 mg), dichlo-
roethane (10 mL), benzaldehyde (5 mmol), naphthalene
(inert internal standard, 0.3 mmol) and then the mixture was
stirred at room temperature. Dioxygen was bubbled through
the solution (10 mL min−1). We sampled during the reaction
and the products were analyzed by GC-FID and GC-MS
analysis.
2 Experimental
3 Results and Discussion
All reagents and solvents were of analytical grade and were
obtained commercially. CuPcTs was prepared and purified
as reported [30]. No impurities were found in the cyclohex-
anone by GC-MS analysis before use.
3.1 Characterization of CoPcTs-Zn2Al-LDH
From the literature [31], coprecipitation at constant pH gener-
ally is a better method for preparing LDHs than directly anion-
exchange procedure. The X-ray powder diffraction patterns
(XRD) is always used to identify the structure of hydrotalcites,
and Fig. 1 shows the XRD patterns of CuPcTs-Zn2Al-LDH
and CO32−-Zn2Al-LDH as comparison. The pattern of
CO32−-Zn2Al-LDH sample shows common features with
reflections located at the angles typical of a hydrotalcite-like
phase: sharp and symmetrical for (003), (006), (110) and
(113), and broad and asymmetrical for (009), (015) and (018),
respectively [32, 33]. In relation to CuPcTs-Zn2Al-LDH sam-
ple containing CuPcTs intercalated in the layers, its XRD pat-
tern is very different from the CO32−-Zn2Al-LDH, but similar
to that of CoTSPP-Zn2Al-LDH [29]: a lower crystallinity and
new peaks observed in the 2θ range 2.5–30° (Fig. 1).
2.1 Synthesis of CuPcTs-Zn2Al-LDH
Typically, the samples were obtained by the coprecipita-
tion of metal nitrates and sodium CuPcTs. A mixture of
Zn(NO3)2·6H2O (1.67 g, 0.0056 mol) and Al(NO3)3·9H2O
(1.05 g, 0.0028 mol) was dissolved in 50 mL of deion-
ized water. The aqueous solution was slowly added with
mechanic stirring to 10 mL of distillated water at 25°C with
sodium CuPcTs (1.51 g, 1.54×10−3 mol); pH=7.5 was
maintained by the continuous addition of 0.1 mol L−1 NaOH.
The resulting suspension was stirred for 24 h at 80°C under
N2 atmosphere. The product was filtered, washed with dis-
tilled water at 80°C and finally dried at room temperature.
According to ICP analysis, the amounts of immobilized
Because of the rhombohedral packing of the LDH unit
cell [34], the (hkl) reflections along the c axis (003) will
1 3

Copper Tetrasulfophthalocyanine Intercalated Hydrotalcite as an Efficient Bifunctional Catalyst for the . . .
3
2−
obtained for the general inorganic anions such as CO3
.
Therefore, the interlayer distance of intercalated material
undergoes a large increase from 7.5 to 22.6 Å following the
intercalation process.
The interlayer space available for intercalated phthalo-
cyanine anions can be estimated similarly to hybrid LDH by
subtracting a thickness of the hydroxide layer (i.e. 4.80 Å)
from the basal spacing supposing that anionic substituents
are arranged between the zinc tetrahedra [22]. The obtained
gallery height of about 17.8 Å is comparable with the cal-
culated dimensions of the copper phthalocyanine molecular
plane (ca. 18×18×5.5 Å) [31]. This spacing allows CuPcTs
to have its long axis oriented nearly perpendicular to the
clay layers, in accordance with that of CuPcTs-Mg2Al-LDH
[34].
Fourier transform infrared spectrometer (FT-IR) was
also used to characterize the CuPcTs-Zn2Al-LDH hybrid.
Figure 2 shows that the characteristic vibration modes
associated with the copper phthalocyanine are present in
the intercalated hybrid between 600 and 800 and 1000–
1500 cm−1 [35, 39]. The sharp stronger band at 1384 cm−1
corresponding to the carbonate anion24 in the Zn2Al hydro-
talcites interlayers disappears in the hybrid, indicating that
CuPcTs has been intercalated intact into the LDH, and no
CO32−-Zn2Al-LDH formed as impurity during the precipita-
tion procedure.
The absorption spectrum of pure solid CuPcTs and
CuPcTs-Zn2Al-LDH both display the Soret band at
352 nm and two Q bands at about 620 and 680 nm, while
CO32‒-Zn2Al-LDH does not exhibit any absorption in these
ranges (Fig. 2). The results further confirm that CuPcTs has
been intercalated into the interlayer of LDH.
Fig. 1 XRD patterns of CO32−-Zn2Al-LDH, CuPcTs-Zn2Al-LDH and
recycled CuPcTs-Zn2Al-LDH
increase with the ABCABC-type stacking. The (00l) peaks
are shifted to lower 2θ values upon incorporation of the
large CuPcTs anion, compared to the pattern of LDH with
2‒
the smaller interlayer CO3 anion. These results indicate
a hydrotalcite structure was formed, which are consistent
with that reported by Carrado [31] and Abellán [35], etc.
All the diffractions can be assigned to pure phases of the
hybrid and no impurities such as Zn(OH)2, Al(OH)3 or
CO32−-Zn2Al-LDH were observed [36], indicating the high
affinity of anionic phthalocyanine toward the hydroxide
layers.
The basal spacing distance of LDHs are actually depen-
dent on the size of anions and their orientation between the
layers. By calculating from the reflection (003), a distance
of 7.5 Å was obtained for CO32−-Zn2Al-LDHs, which is
typical for hydrotalcite-like materials containing carbonate
anions [37]. Considering the same crystalline system used
to assign the LDH peaks, one could calculate the hybrid
LDH’s interlayer distance of 22.6 Å, much higher than that
The crystal morphologies of the prepared samples were
investigated with scanning electron microscopy (SEM). The
SEM images in Fig. 3 show that both of CO32−-Zn2Al-LDH
and CuPcTs-Zn2Al-LDH formed plate-like agglomerated
crystals, representing the character of layered materials [41,
42].
Fig. 2 FTIR and DR UV-Vis
spectra of CO32−-Zn2Al-LDH,
CuPcTs-Zn2Al-LDH and
CuPcTs
1 3

4
W. Zhou et al.
Fig. 3 SEM images of
CO32−-Zn2Al-LDH (a) and
CuTSPP-Zn2Al-LDH (b)
In summary, these characterizations presented above
show that CuPcTs has been successfully intercalated
into the interlayer of ZnAl hydrotalcite and plate-like
agglomerated crystals formed. And the inductively
coupled plasma-optical emission spectrometry (ICP-
OES) indicated the amount of intercalated CuPcTs was
2.3 × 10−4 mol g−1.
Table 1 B-V oxidation cyclohexnaone under different reaction condi-
tions in the presence of benzaldehyde
Entry
Catalyst
Solvent
Ra
Yieldb
(%)
1
2
3
4
5
6c
7
8
9
No catalyst
DCE
DCE
DCE
DCE
DCE
DCE
DCM
CYH
ACN
2.5
2.5
2.5
2.5
2
34
74
CuPcTs-Na
CO32‒-Zn2Al-LDH
CuPcTs-Zn2Al-LDH
CuPcTs-Zn2Al-LDH
CuPcTs-Zn2Al-LDH
CuPcTs-Zn2Al-LDH
CuPcTs-Zn2Al-LDH
CuPcTs-Zn2Al-LDH
67
>99
92
3.2 Catalytic Performance of CuPcTs-Zn2Al-LDH in
B-V Oxidation
3
>99
95
2.5
2.5
2.5
The catalytic activity of the CuPcTs-Zn2Al-LDH for the
B-V oxidation was examined by performing the oxidation
of cyclohexanone to ε-caprolactone in the presence of benz-
aldehyde at room temperature. Before discussing the cata-
lytic performance of the prepared catalyst, varied solvent
including dichloroethane (DCE), dichloromethane (DCM),
cyclohexane (CYH) and acetonitrile (ACN), were first opti-
mized. The influence of the solvent on the catalytic activity
is mainly related to the polarity, and DCE having the appro-
priate polarity exhibited the best result (Table 1).
Under the optimized reaction conditions, the conversion
of cyclohexanone and selectivity of ε-caprolactone are all
near to 100% after 7 h over CuPcTs-Zn2Al-LDH. The blank
reaction without catalyst showed even low conversion,
indicating that the prepared hybrid performed as catalyst
in the reaction. CuPcTs-Na4 and CO32‒-Zn2Al-LDH have
also been investigated in the B-V oxidation as comparision,
and the intercalated sample exhibited the obviously higher
catalytic performance. The product yield reached over
99% when 2.5 equiv. of benzaldehyde was used, indicating
that aldehyde efficiency is higher than those in previously
reported studies [12, 19, 22].
34
16
General conditions: cyclohexanone 2 mmol, catalyst 8.0 mg, reaction
time 7 h, room temperature, O2 10 mL min−1
aEquivalent amount of benzaldehyde
bThe selectivities were all >99%
cReaction time 6 h
and the selectivities were above 99%. XRD pattern for the
reused catalyst suggested that the layered structure was
completely preserved after several reuses (Fig. 1).
The turnover frequency (TOF) of active site is always
used for the precise comparison of the activity of different
catalysts. Some characteristic data of other catalytic systems
based on O2/benzaldehyde in the B-V oxidation of cyclo-
hexanone are collected in Table 2. It can be observed that
the prepared CuPcTs-Zn2Al-LDH exhibits higher TOF than
most of these catalytic systems. Although FePcS-SiO2 [12]
(Table 2, entry 2) and MnAlPO (Table 2, entry 11) showed
higher TOF, but the conversions were low and only mod-
erate yields were obtained. Even doubling the FePcS-SiO2
catalyst amount, the conversion increased only slightly with
the selectivity decreasing below 90%. The catalytic rate is
also lower than our previous reported CoTSPP-Zn2Al-LDH
catalyst (Table 2, entry 8) [29], but the reaction conditions
are milder and the efficiency of benzaldehyde increases.
Jeong et al. [46] have reported a metalloporphyrins bridged
periodic mesoporous organosilicas, and excellent catalytic
activitywasobservedintheB-Voxidationofcyclohexanone.
In addition, the reaction temperature is lower than typi-
cal reported work [12–22] including the metalloporphyrin
intercalated hydrotalcites [29], where reaction temperatures
higher than 40°C were always employed.
Subsequently,therecyclabilityoftheCuPcTs-Zn2Al-LDH
was examined in the aerobic oxidation of cyclohexanone
with shorter reaction time (6 h). The catalyst showed no
appreciable reduction of activity even after six runs (Fig. 4),
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Copper Tetrasulfophthalocyanine Intercalated Hydrotalcite as an Efficient Bifunctional Catalyst for the . . .
5
Table 3 B-V Oxidation of various ketones over CuPcTs-Zn2Al-LDH
in the presence of benzaldehyde
Entry
1b
Substrate
Producta
t (h) Yield (%)d
O
O
O
8
92 [50]
2
3
O
O
O
9
88 [51]
O
7
O
O
>99 [52]
>99 [53]
4
O
O
O
14
Fig. 4 Reusability of CuPcTs-Zn2Al-LDH for B-V oxidation. General
conditions: cyclohexanone 2 mmol, equivalent amount of benzalde-
hyde 2.5, catalyst 8.0 mg, reaction time 6 h, room temperature, O2
10 mL min−1
O
O
O
5
6
8
9
97 [54]
Table 2 The main results of other catalytic systems based on
O2/benzaldehyde in the B-V oxidation of cyclohexanone
O
O
O
>99 [55]
Entry
1
Catalyst
Ca
(%)
Sb
(%)
TOF Ref.
(h−1
)
(51%)
(49%)
O
O
CuPcTs-Zn2Al-LDH
155
This
work
>99
>99
2
FePcS-SiO2
Co3O4
61
100
100
100
400
4
[12]
[14]
[16]
[17]
[20]
[24]
[29]
[43]
[44]
[45]
7
O
O
O
14
>99 [56]
3
98
4
InOx/TUD-1
L-BIOXc
100
>98d >98d
9
5
33
20
36
298
23
12
257
(53%)
(47%)
6
Ni-Co-HMS-X
CO32‒-Mg3AlFe0.3-LDH 100
100
100
100
>99
43.1
>99
98
O
O
7
8
CoTSPP-Zn2Al-LDH
>99
9
[H4TPP][HPW12O40]
Fe-Sn-O mixed oxides
MnAlPO
56.1
96.6
78
8
O
O
10
16
Trace
10
11
O
O
O
9c
84 [57]
aConversion of cyclohexanone
bSelectivity of ε-caprolactone
cBiogenous iron oxides
O
O
O
dYield of ε-caprolactone product
O
10c
11b
18
30
65 [58]
38 [59]
O
O
However, their catalytic activities for the substrates with
increasing bulkiness were even low, and only a 50% con-
version was obtained for 2-methylcyclohexanone.
O
O
O
In summary, from the above results and analysis, it is
clear that CuPcTs intercalated hydrotalcite is an efficient
catalyst for the B-V oxidation through O2/aldehyde system.
Encouraged by these results, we have carried out
CuPcTs-Zn2Al-LDH catalyzed B-V oxidation of a vari-
ety of ketones to better understand both the scope and the
generality of the reaction. Table 3 shows the B-V type
aerobic oxidation of various ketones in the presence of
General conditions: substrate 2 mmol, catalyst 8.0 mg, room tem-
perature, 2.5 equiv. of benzaldehyde, O2 10 mL min−1
aData in brackets are the selectivity of corresponding product
bReaction temperature was 40°C
cReaction temperature was 30°C
dThe characterization of the products can be found in the reference
1 3

6
W. Zhou et al.
Fig. 5 a Oxidation of benzaldehyde to peracid (m-chlorobenzaldehyde 2 mmol, O2 10 mL min−1, catalyst 8.0 mg, room temperature) and b Oxida-
tion of cyclohexanone by m-chloroperbenzoic acid (substrate 2 mmol, catalyst 8.0 mg, room temperature, 2.5 equiv. of m-chloroperbenzoic acid)
Scheme 1 The proposed
reaction mechanism of the
B-V oxidation catalyzed by
CuPcTs-Zn2Al-LDH
CuPcTs-Zn2Al-LDH and benzaldehyde. Cyclobutanone,
cyclopentanone, cyclohexanone and 4-methylcyclohexa-
none (Table 3, entries 1‒4) were successfully oxidized
with high conversion and selectivity. A good yield was also
observed when pinacolin was used as substrate (Table 3,
entry 5). From asymmetrical ketone like 3-methylcyclo-
hexanone, similar yields of 5-methyl-ε-caprolactone and
3-methyl-ε-caprolactone were obtained (Table 3, entry 6),
similar results was also obtained for 2-methylcyclohexa-
none (Table 3, entry 7), which is different from most of the
reported results [13, 29]. However, for the linear ketone
like 4-methyl-2-pentanone, the catalytic system is not valid
under such conditions (Table 3, entry 8).
Finally, some phenyl containing substrates have been
introduced into the reaction system. For the p-methoxyace-
tophenone (Table 3, entry 9), a high 84% yield was obtained
when the temperature increased to 30°C. Although the yield
was a little lower than that reported by Kaneda [47], the
reaction temperature was lower and the catalyst amount was
reduced with higher selectivity. In addition, the benzyl phe-
nyl ketone and diphenyl ketone (Table 3, entries 10 and 11),
which were only investigated in the presence of peroxide
[48, 49], could be smoothly transformed under the selected
reaction conditions. Interestingly, although no chemose-
lectivity was observed in the 2-methylcyclohexanone and
3-methylcyclohexanone, only one product formed for the
oxidation of benzyl phenyl ketone (which was confirmed
by the fact that only benzyl alcohol and benzoic acid were
observed in the hydrolyzed products), clearly indicating that
CuPcTs-Zn2Al-LDH could impart chemoselectivity in high
degree for these phenyl containing substrates.
Although the reaction rate depends on the chemical
structure of ketones, it can be concluded that the prepared
CuPcTs-Zn2Al-LDH catalysts can oxidize various ketones
to corresponding lactones or esters under such mild reaction
conditions.
To validate our design from the viewpoint of the cat-
alytic mechanism and investigate whether the hybrid
CuPcTs-Zn2Al-LDH can catalyze both steps of B-V oxi-
dation, a series of controlled reactions have been per-
formed. Firstly, CuPcTs-Zn2Al-LDH was introduced into
the first reaction step, namely the oxidation of aldehyde
to peracid. For the easy analysis of peracid, m-chloro-
benzaldehyde instead of benzaldehyde was used and
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Copper Tetrasulfophthalocyanine Intercalated Hydrotalcite as an Efficient Bifunctional Catalyst for the . . .
7
Acknowledgments This work was supported by the National Natu-
ral Science Foundation of China (Grant No. 21403018), Top-notch
Academic Programs Project of Jiangsu Higher Education Institutions,
and Prospective Joint Research Project on the Industry, Education and
Research of Jiangsu Province (BY2015027-16).
m-CPBA was quantified by titration. From the Fig. 5a,
it can be observed that the oxidation of benzaldehyde to
perbenzoic acid can happen through autoxidation. And
both CuPcTs-Zn2Al-LDH and CO32‒-Zn2Al-LDH could
accelerate the reaction, whilst CuPcTs-Zn2Al-LDH exhib-
ited higher activity. On the other hand, the hybrid LDH
has also been introduced into the second step using
m-CPBA as the oxidant, while the blank experiments
under the same conditions were performed as comparison.
CuPcTs-Zn2Al-LDH and CO32‒-Zn2Al-LDH showed com-
parable activity in the reaction (Fig. 5b), because the cata-
lytic performance of hydrotalcites for this step is mainly
related to their basicity [22]. It is obviously concluded that
CuPcTs-Zn2Al-LDH could accelerate both of the reactions
and act as the bifunctional catalyst for the B-V oxidation
under the selected conditions.
On the basis of the above results and analysis, we sup-
pose that, in the CuPcTs-Zn2Al-LDH catalyzed B-V oxi-
dation of ketones by the O2/aldehyde system, the hybrid
not only catalyzed the oxidation of aldehyde to form the
peroxyacid, but also accelerated the reaction of ketone
with peroxyacid to corresponding product. A possible
mechanism was proposed in Scheme 1 based on our obser-
vations and reported results [22, 60, 61]. Perbenzoic acid
is firstly formed with oxygen under the catalysis of cop-
per phthalocyanine. Then the reaction of the peroxyacid
with OH group on the hydrotalcite surface gives a metal
perbenzoate species and H2O. Then, the perbenzoate spe-
cies attacks ketone to form a metal alkoxide intermediate,
which further converts into lactone accompanied with the
formation of benzoic acid anion. After reacting with H2O,
benzoic acid is produced and Zn Al hydrotalcite having
OH groups is recovered.
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A bifunctional catalyst has been designed and prepared by
intercalation of CuPcTs into ZnAl hydrotalcite on the basis
of the reaction mechanism of B-V oxidation. Varied charac-
terizations of the sample indicated that CuPcTs has been suc-
cessfully introduced into the interlayer of ZnAl hydrotalcite.
The material could smoothly catalyze the B-V type oxidation
from ketones to corresponding lactones or esters in the pres-
ence of benzaldehyde, and tolerated a wide range of sub-
strates. The catalyst recycling tests suggest that the durability
of the CuPcTs-Zn2Al-LDH is quite good in the tested reac-
tion conditions. The controlled experiments have revealed
that the prepared hybrid could catalyze both the oxidation of
benzaldehyde to peroxyacid and the formation of lactones or
esters, indicating its bifunctional role in B-V oxidations. The
protocol would be helpful in the rational design of environ-
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