Synthesis, characterization, and catalytic activity of sulfonic acid-functionalized periodic mesoporous organosilicas

Article abstract of DOI:10.1016/j.jcat.2004.09.007

Sulfonic acid-functionalized periodic mesoporous organosilicas were synthesized directly by cocondensation of (R′O)₃SiRSi(OR′ )₃ (R = CH₂CH₂ and C₆H₄; R′ = CH₃ and C₂H₅) with 3-mercaptopropyltrimethoxysilane (MeO)₃SiCH₂CH ₂CH₂SH in the presence of H₂O₂ using nonionic oligomeric polymer surfactant C₁₈H₃₇(OCH ₂CH₂)₁₀OH in acidic medium. The sulfonic acid functionalities (SO₃H) were generated in situ by oxidation of the propylthiol using H₂O₂ as oxidant during the synthesis process. Powder X-ray diffraction patterns and nitrogen sorption indicate the formation of well-ordered mesoporous material with uniform porosity. The highest acid-exchange capacity (acid-base titration methods) was 1.72 H⁺ mmol/g. Complete oxidation of SH to SO₃H was observed as evidenced by X-ray photoelectron spectroscopy. For comparison, the sulfonic acid-functionalized mesoporous organosilicas were also prepared by a grafting method. The catalytic properties of the materials were investigated in liquid-phase condensation of phenol with acetone to form Bisphenol A. All sulfonic acid-functionalized mesoporous organosilicas show high catalytic activity. The highest TOF obtained for the mesoporous organosilica is 17.2.

Full text of DOI:10.1016/j.jcat.2004.09.007

Journal of Catalysis 228 (2004) 265–272
www.elsevier.com/locate/jcat
Synthesis, characterization, and catalytic activity of sulfonic
acid-functionalized periodic mesoporous organosilicas
a,∗
a
a
b
b
a
Qihua Yang , Jian Liu , Jie Yang , Mahendra P. Kapoor , Shinji Inagaki , Can Li
a
State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
b
Toyota Central R&D Laboratories, Inc., Nagakute, Aichi 480-1192, Japan
Received 26 May 2004; revised 27 August 2004; accepted 3 September 2004
Abstract
ꢀ
ꢀ
3
Sulfonic acid-functionalized periodic mesoporous organosilicas were synthesized directly by cocondensation of (R O) Si–R–Si(OR )
3
ꢀ
(
R = CH CH and C H ; R = CH and C H ) with 3-mercaptopropyltrimethoxysilane (MeO) SiCH CH CH SH in the presence of
2
2
6
4
3
2
5
3
2
2
2
H O using nonionic oligomeric polymer surfactant C
H (OCH CH ) OH in acidic medium. The sulfonic acid functionalities (–SO H)
2
2
18 37 2 2 10 3
were generated in situ by oxidation of the propylthiol using H O as oxidant during the synthesis process. Powder X-ray diffraction patterns
2
2
and nitrogen sorption indicate the formation of well-ordered mesoporous material with uniform porosity. The highest acid-exchange capacity
+
(
acid–base titration methods) was 1.72 H mmol/g. Complete oxidation of –SH to –SO H was observed as evidenced by X-ray photoelectron
3
spectroscopy. For comparison, the sulfonic acid-functionalized mesoporous organosilicas were also prepared by a grafting method. The
catalytic properties of the materials were investigated in liquid-phase condensation of phenol with acetone to form Bisphenol A. All sulfonic
acid-functionalized mesoporous organosilicas show high catalytic activity. The highest TOF obtained for the mesoporous organosilica is 17.2.

2004 Elsevier Inc. All rights reserved.
Keywords: Sulfonic acid; Mesoporous bifunctional organosilica; Ethane bridged; Phenylene bridged; Bisphenol A
1
. Introduction
[6] reported bifunctionalized periodic mesoporous organosi-
licas (BPMOs) having bridging ethyl groups in the walls
and vinyl groups protruding into the channels. Later, a se-
ries of organic functionalities such as amine, thiol, diamine,
imidazole, pyridine, benzyl, and phenethyl were incorpo-
rated into the channel of mesoporous organosilicas with the
bridging ethyl groups in the framework [7]. In all reports
basic medium along with cationic surfactant was employed.
Markowitz and co-workers tried the synthesis of BPMOs in
acidic medium using cetyltrimethylammonium chloride as
surfactants [8]. Unfortunately, they could not succeed in get-
ting the mesoporous structures. Still the study demonstrated
that larger amounts of functional groups could be incorpo-
rated into the mesoporous organosilicas in acidic medium.
The synthesis of ordered mesoporous material with high
concentrations of functional groups is very important for ap-
plications. Recently, nonionic oligomeric surfactants were
also successfully used for the synthesis of PMOs in acidic
The periodic mesoporous organosilicas (PMOs) attracted
much attention and were recognized as potential candi-
dates for applications in catalysis, enantioselective separa-
tion, chromatography, and sensing. PMOs synthesized from
ꢀ
ꢀ
bridged organosilane precursors, (R O)3Si–R–Si(OR )3,
have uniformly distributed organic moiety in the framework.
To date, only a limited number of organic moieties have been
incorporated in the PMOs framework such as ethane, ethyl-
ene, benzene, biphenylene, and thiophene [1–5]. A versatile
approach for the functionalization of PMOs is the devel-
opment of bifunctionalized PMOs by cocondensation of
trialkoxyorganosilanes with bridged silsesquioxane precur-
sor in the presence of the surfactant. Ozin and co-workers
*
Corresponding author. Fax: +86 411 4694447.
E-mail address: yangqh@dicp.ac.cn (Q. Yang).
0021-9517/$ – see front matter  2004 Elsevier Inc. All rights reserved.
doi:10.1016/j.jcat.2004.09.007

266
Q. Yang et al. / Journal of Catalysis 228 (2004) 265–272
medium [9,10]; however, these surfactants have not yet been
employed for the synthesis of BPMOs.
2.2. Synthesis of sulfonic acid-functionalized mesoporous
organosilicas
Sulfonic acid-functionalized mesoporous silicas have
been successfully applied in a number of acid-catalyzed
reactions, such as esterification and condensation [11–13].
Introducing sulfonic acid groups to PMOs is interesting
since the surface properties (hydrophobicity/hydrophilicity)
of PMOs can be modified by simply varying the nature of
the bridging organic group in the framework. Recently, we
have reported the sulfonic acid-functionalized mesoporous
organosilicas by cocondensation of phenyl-bridged precur-
sor [(EtO)3Si–C6H4–Si(OEt)3] and 3-mercaptopropyltri-
methoxysilane [MPTMS: (MeO)3Si–CH2CH2CH2SH] in
the presence of octadecyltrimethylammonium chloride
2.2.1. Direct synthesis of sulfonic acid-functionalized
ethane silica (EPMO)
Brij-76 (1.0 g) was dissolved in HCl solution (16 g,
◦
2 M) at 50 C under vigorous stirring. A mixture of BTME
(3.5 mmol) and MPTMS (1.5 mmol) was added to the above
solution, followed by slow addition of H2O2 (8 g). The re-
◦
action mixture was kept stirring at 50 C for 24 h. After
filtration, the white precipitate was recovered by filtration
followed by thoroughly washing with deionized water. The
solid was dried at room temperature. The surfactant was
extracted by refluxing 0.5 g of as-synthesized material in
200 ml ethanol for 12 h. The sulfur contents of the sample
are listed in Table 2.
[
C18TMACl] surfactant followed by postsynthesis oxida-
tion of –SH to –SO3H using concentrated HNO3 as oxi-
dant [14]. The postsynthesis oxidation method always leads
to incomplete oxidation of –SH [15] and also the oxidation
process using HNO3 as oxidant is vigorous and accompa-
nied by the generation of NO2. In situ generation of –SO3H
groups using H2O2 as oxidant in acidic medium was also
reported [16].
2.2.2. Direct synthesis of sulfonic acid-functionalized
benzene silica
The synthesis procedure was similar to that described
above. A mixture of BTEB (3.5 mmol) and MPTMS
(1.5 mmol) was used along with 0.8 g Brij-76. The sulfur
contents of the sample are listed in Table 2.
Here, we report the direct synthesis of the sulfonic acid-
functionalized mesoporous organosilicas with high con-
centrations of –SO3H functionalities by cocondensation
of ethane- or benzene-bridged organosilane with 3-mer-
captopropyltrimethoxysilane in the presence of H2O2 us-
ing nonionic oligomeric polymer surfactant (Brij-76) in
acidic medium. The catalytic activity of these sulfonic acid-
functionalized mesoporous organosilicas was tested for the
liquid-phase condensation of phenol with acetone to form
Bisphenol A, which is a very important raw material for
synthesis of resins and polymers. In the industrial process,
ion-exchanged resins are used as catalysts for the synthe-
sis of Bisphenol A. However the thermal stability of resins
is limited. The search for effective solid acids with high
thermal stability continues. It was found that the sulfonic
acid-functionalized mesoporous organosilicas synthesized
in this work show high catalytic activity and stability. It
was shown by others [17,18] that PMOs exhibit very good
mechanical and hydrothermal stability. These new materi-
als could serve as solid acid catalysts with potential in many
acid-catalyzed reactions.
2.2.3. Preparation of sulfonic acid-functionalized
organosilicas by grafting
In a typical grafting procedure, MPTMS (2 mL) was
added dropwise into the previously dispersed mesoporous
benzene silica [3] or ethane silica [1] mesoporous mater-
ial (1.28 g) in chloroform (100 mL). The suspension was
stirred at room temperature for 5 consecutive days. The
thiol-functionalized mesoporous organosilica material ob-
tained after filtration was washed with copious amounts of
chloroform and dried at room temperature. The transforma-
tion of –SH to –SO3H was accomplished by treatment of
thiol-functionalized ethane silica and benzene silica with 65
wt% HNO3 [14] to give GEPMO and GBPMO, respectively.
The sulfur contents of the samples are listed in Table 2.
2.3. Catalytic experiment
The liquid-phase condensation of phenol with acetone to
form Bisphenol A was performed in a 50-mL sealed glass
vessel. A mixture of phenol (70 mmol), acetone (10 mmol),
◦
and catalyst (70 mg) was stirred at 85 C for 24 h. After
2
. Experimental
the reaction, biphenyl solution in acetonitrile was added as
an external standard. The mixture was filtered and the fil-
trate was analyzed on an Agilent 6890 gas chromatograph
equipped with a flame ionization detector and a HP-5 cap-
illary column (30 m × 0.25 mm × 0.25 µm). The product
identification was performed using standard compounds.
2
.1. Chemicals and reagents
All materials were analytical grade and used as purchased
without further purification. 3-Mercaptopropyltrimethoxysi-
lane, C18H37(OCH2CH2)10OH [Brij-76], and 1,2-bis(trime-
thoxysilyl)ethane [BTME] were purchased from Sigma-
Aldrich Company Ltd. (USA). 1,4-Bis(triethoxysilyl)ben-
zene [BTEB] was synthesized according to the litera-
ture [19].
2.4. Characterization
X-ray powder diffraction (XRD) patterns were recorded
on a Rigaku D/Max 3400 powder diffraction system using

Q. Yang et al. / Journal of Catalysis 228 (2004) 265–272
267
CuKα radiation. The nitrogen sorption experiments were
are nontoxic, biodegradable, and inexpensive. Their ef-
fective use in the synthesis of mesoporous ethane silicas
with well-ordered hexagonal structures was already demon-
strated [9,10]. In the present study non-ionic oligomeric
alkylethylene oxide surfactants [Brij-76] in acidic medium
in combination with in situ generation of –SO3H groups
were investigated. The hydrolysis and condensation of the
performed at 77 K on an ASAP 2000 system. The samples
◦
were evacuated at 100 C for 10 h prior to the measurement.
BET surface area was calculated from adsorption data in
the relative pressure range from 0.01 to 0.3. Pore diameters
were determined from adsorption branches using the Barret–
Joyner–Halenda (BJH) method. The solid-state NMR spec-
tra were obtained with a Bruker DRX 400 spectrometer
equipped with a magic-angle spin probe using a 4-mm ZrO2
rotor. 13C (100.6 MHz) cross-polarization magic-angle spin-
ning (CP-MAS) spectra were measured under experimental
conditions of 5-ms contact time, 3-s pulse delay, and 7.0 kHz
spin rate. X-ray photoelectron spectra (XPS) were measured
on VG ESCALAB MK-2 X-ray spectrometer equipped with
a hemispherical electron analyzer and an Al anode X-ray ex-
citing source (AlKα energy = 1486.6 eV). Binding energies
were corrected for charge effects by referencing to the C1s
peak at 284.6 eV. Thermal gravimetric analysis (TGA) was
performed with Perkin–Elmer Pyris Diamond TG analyzer
organosilane precursor in the presence of H O enable
2
2
the formation of highly ordered mesoporous EPMO and
BPMO with high concentrations of –SO H functionalities
3
(Scheme 1). The structural, textural, and compositional in-
formation including the titration results of both sulfonic
acid-functionalized mesoporous organosilicas are listed in
Table 1. The results on sulfonic acid-functionalized meso-
porous organosilicas synthesized using grafting are also in-
cluded.
3
.2. Mesostructure and porosity
◦
under nitrogen atmosphere with a heating rate of 10 C/min.
Powder X-ray diffraction patterns of surfactant-free sul-
The acid-exchangecapacity was determined by titration with
NaOH. In a typical procedure, 0.1 g of solid was suspended
in 20 g of 2 M aqueous NaCl solution. The resulting sus-
pension was stirred at room temperature for 24 h until equi-
librium was reached and potentiometrically titrated by drop-
wise addition of 0.1 M NaOH.
fonic acid-functionalized benzene silica display three re-
flection peaks, indicating the formation of a well-ordered
two-dimensional hexagonal structure (Fig. 1a). A very small
◦
and broad peak centered around 12 2θ with a d spac-
ing of 0.76 nm was also observed, suggesting the exis-
tence of some periodicity in the pore walls. Similar pore
wall periodicity reported previously [3,14] was attributed to
the organization of benzene moiety bridged in the meso-
porous framework in basic medium. However, the extent
of periodicity observed in the case of BPMO synthesized
under acidic medium is lower than that in similar mate-
rials synthesized under basic conditions. A similar ten-
dency of the periodicity was also observed for the rela-
tively large-pore benzene-bridged mesoporous organosil-
icas synthesized with triblock copolymer surfactants in
3
. Results and discussion
3
.1. Preparation of sulfonic acid-functionalized
mesoporous organosilicas
Non-ionic oligomeric alkylethylene oxide surfactants
are useful because of their high interfacial stability. They
Scheme 1. Direct synthesis of sulfonic acid-functionalized mesoporous organosilicas.
Table 1
Structural, textural, and compositional information of sulfonic acid-functionalized organosilicas
Sample
d
BET surface area
(m /g)
Pore diameter
(nm)
Total pore volume
(cm /g)
a
0
(nm)
Wall thickness
(nm)
1
00
2
a
3
b
c
(nm)
EPMO
BPMO
GEPMO
GBPMO
6.05
5.77
5.10
4.69
1401
1056
756
3.10
3.50
2.39
2.10
1.11
0.88
0.52
0.41
6.99
6.66
5.89
5.41
3.89
3.16
3.50
3.31
665
a
Pore diameter was calculated from adsorption branch.
√
b
c
a = 2d
/
3.
0
100
Wall thickness = a -pore size.
0

268
Q. Yang et al. / Journal of Catalysis 228 (2004) 265–272
Table 2
walls. It is noteworthy that the additional broad reflection at
◦
Comparison of sulfur content in organosilicas prepared by a cocondensation
method and a grafting method
2
0 2θ (d = 0.42 nm), that was also observed in the original
mesoporous benzene silica is not due to any contamination
of the amorphous materials but due to the amorphous nature
of atomic arrangements of Si and O in the silica layers of
the benzene silica materials. The XRD pattern of GEPMO
Sample
Initial mole percent of MPTMS
mol%)
S content
(wt%)
a
(
EPMO
BPMO
GEPMO
GBPMO
30
30
–
5.5
3.3
2.6
2.8
(
Fig. 2b) is almost similar to that reported for the meso-
porous ethane silica.
–
The nitrogen adsorption isotherms of sulfonic acid-
functionalized organosilicas (BPMO and EPMO) were of
type IV with a typical capillary condensation step in the
relative pressure (P/P0) range of 0.3–0.5 (Fig. 3). This in-
dicates that both BPMO and EPMO possess well-defined
mesoporous structures and relatively narrow pore-size dis-
tributions. Similar type IV isotherms were also observed for
GEPMO and GBPMO, indicating that the mesostructures
survived both the grafting and the oxidation process. It is
worth noting that EPMO and BPMO synthesized directly in
acidic medium show higher BET surface areas and larger
pore diameters than the samples prepared by grafting (Ta-
ble 1).
a
Sulfur contents were obtained by elemental analysis.
3
.3. Compositional and structural information in the
framework
Fig. 1. XRD patterns of surfactant-free sulfonic acid-functionalized
organosilicas synthesized in acidic medium in the presence of H O :
2
2
Four resonances were observed in 13C CP MAS NMR
(a) BPMO; (b) EPMO.
spectrum of EPMO (Fig. 4). The resonance at 5.9 ppm
is due to the C species of ethane moiety [1] while the
resonance at 12.5, 19.1 and 54.6 ppm are assigned to
1
2
3
1
2
3
C, C, and C carbon species of ≡Si– CH2 CH2 CH2–
SO3H, respectively (Fig. 4a) [16]. The 13C NMR spec-
trum of BPMO displays the signal of benzene moiety at
1
33.2 ppm [3]. Signals coming from the propylsulfonic
1
2
acid moiety appeared at 13.0 ( C), 18.9 ( C), and 54.8
3
(
C) ppm [14]. The signal at 30.4 ppm may be due to
1
3
the residue surfactant (Fig. 4b). C CP MAS NMR spec-
tra of both GEPMO and GBPMO synthesized by grafting
method are shown in Fig. 5. For GBPMO, the signals of
1
2
3
carbon species of ≡Si– CH2 CH2 CH2–SO3H and -Ph-
were clearly observed with almost the same chemical shift
2
Fig. 2. XRD patterns of sulfonic acid-functionalized organosilicas prepared
by grafting (a) GBPMO; (b) GEPMO.
as that of BPMO. For GEPMO; the signals of C and
3
1
2
3
C of ≡Si– CH2 CH2 CH2–SO3H appeared at 19.1 and
5
4.6 ppm, respectively. The broad peak centered at 5.9 ppm
1
1
2
3
acidic medium [20]. The X-ray patterns of ethane-bridged
organosilicas (EPMO) clearly exhibit one diffraction peak
indicating that the material has an ordered mesostructure
masks the C carbon of ≡Si– CH CH CH –SO H and
2
2
2
3
13
carbon of the –CH CH –moiety. C CP MAS NMR re-
2
2
sults clearly demonstrate the integrity of propylsulfonic
acid functionality on the mesoporous organosilicas synthe-
sized by both the cocondensation method and the grafting
method.
X-ray photoelectron spectroscopy analyses of surfactant-
free BPMO and EPMO are shown in Fig. 6. S2p binding
energy was found to be 169.2 and 169.3 eV for BPMO and
EPMO, respectively. This binding energy was attributed to
the oxidized sulfur (–SO3H) [21]. No S2p binding energy at
164 eV (corresponding to –SH) was observed, further con-
firming the complete oxidation of –SH to –SO3H. The O1s
(
Fig. 1b).
The X-ray diffraction pattern of GBPMO (Fig. 2a) re-
sembles the parent mesoporous benzene silica reported else-
where [3] that was prepared under basic conditions. In addi-
tion to a peak in the lower angle diffraction regime (2θ <
◦
◦
1
0 ), three additional peaks at 12, 23, and 35 2θ (with
d spacings of 0.76, 0.38, and 0.25 nm) also appeared in
the medium-angle diffraction regime (10 < 2θ < 40). These
peaks are assigned to a periodic arrangement of hydrophobic
benzene layers and hydrophilic silica layers within the pore

Q. Yang et al. / Journal of Catalysis 228 (2004) 265–272
269
Fig. 3. Nitrogen sorption isotherms of surfactant free sulfonic acid-functionalized organosilicas synthesized in acidic medium in the presence of H O :
2
2
(a) BPMO; (b) EPMO.
1
3
Fig. 4. C CP MAS NMR spectra of surfactant-free sulfonic acid-functionalized organosilicas synthesized in acidic medium in the presence of H O . ∗ Refers
2
2
to –OCH CH formed during the surfactant removal process; " refers to spinning side band: (a) EPMO; (b) BPMO.
2
3
13
Fig. 5. C CP MAS NMR spectra of sulfonic acid-functionalized organosilicas synthesized by grafting method. " Refers to the side band: (a) GEPMO;
b) GBPMO.
(
binding energy was found at 532.3 eV for both BPMO and
EPMO while the Si2p biding energy at 102.7 eV for BPMO
and 102.8 eV for EPMO was obtained from an overlap of
Si2p3/2 and Si2p1/2 binding energy. XPS results imply that
the oxidation during the synthesis process lead to complete
oxidation of –SH to –SO3H.
3.4. Thermogravimetric properties
Thermogravimetric analysis of sulfonic acid-functiona-
lized mesoporous organosilicas was conducted from 30 to
◦
900 C under nitrogen atmosphere (Fig. 7). A weight loss
◦
below 120 C was observed for all materials, which is due

270
Q. Yang et al. / Journal of Catalysis 228 (2004) 265–272
Fig. 6. S2p XPS binding energy peak of sulfonic acid-functionalized organosilicas synthesized in acidic medium in the presence of H O : (a) EPMO;
2
2
(b) BPMO.
Fig. 7. Representative thermogravimetric weight loss curves for sulfonic acid-functionalized organosilicas under nitrogen flow: (a) EPMO; (b) BPMO;
c) GEPMO; (d) GBPMO.
(
to the removal of the physisorbed water. Minor weight loss
in the range of 120 to 210 C was observed for EPMO
The decomposition of propylsulfonic acid functionality oc-
◦
◦
curred at 380 C for all materials [16]. The weight loss in
◦
and BPMO synthesized by cocondensation. This weight loss
could be assigned to the decomposition of the surfactant
residue. No weight loss in this range was found for GEPMO
and GBPMO synthesized by a grafting method, indicat-
ing complete removal of the surfactant in these materials.
the range of 400–800 C is due to the decomposition of the
propylsulfonic acid residue and the bridged organic moiety.
Thermogravimetric analysis results reveal that the sulfonic
acid-functionalized mesoporous organosilicas are stable up
◦
to 380 C in a nitrogen flow atmosphere.

Q. Yang et al. / Journal of Catalysis 228 (2004) 265–272
271
Scheme 2. Condensation of phenol with acetone to form Bisphenol A.
3
.5. Catalytic condensation of phenol with acetone to form
Table 3
Acidity and catalytic properties of sulfonic acid-functionalized mesoporous
organosilicas in the catalytic condensation of phenol with acetone to form
Bisphenol A
Bisphenol A
a
To evaluate the catalytic properties of sulfonic acid-
functionalized mesoporous organosilicas and to investigate
the influence of the bridging ethane or benzene moieties, the
condensation of phenol with acetone to form Bisphenol A
was performed (Scheme 2). The effect of the preparation
method on the catalytic properties was evaluated by com-
paring sulfonic acid-functionalized mesoporous organosili-
cas synthesized by cocondensation and grafting. All sulfonic
acid-functionalized mesoporous organosilicas were efficient
catalysts for the condensation of phenol with acetone (Ta-
ble 3). The active site for the reaction is the –SO3H group.
The surface area and average pore diameter of the mate-
rials may also cause the different catalytic activity. There-
fore the acidity of the materials was normalized with the
surface area (Table 3). From the TOF, it can be seen that
the samples (GEPMO and GBPMO) prepared by grafting
exhibit higher catalytic activity than samples (EPMO and
BPMO) synthesized by cocondensation in acidic medium.
The acidity of the materials based on surface area is in the
range of 0.9 × 10 to 1.4 × 10 mmol H /m , which
cannot explain the significant difference of activities. The
diffusion of the reactants and products during the reaction
process may be one of the main reasons for different activ-
ities of the materials. The functionalities introduced to the
mesoporous material by grafting always lead to irregularly
distributed functionalities, and thus most of the functionali-
ties are distributed on the surface or near the pore mouth of
the mesoporous material [22]. The higher catalytic activity
of GEPMO and GBPMO may be due to the fact that sul-
fonic acid sites on the surface or near the pore mouth are
easily accessible for the reactants in the catalytic reactions.
In contrast, mesoporous organosilicas synthesized by cocon-
densation have uniformly distributed sulfonic acid sites. In
addition it might be that the reactants cannot reach some of
the sulfonic acid sites buried in the wall of the materials syn-
thesized by cocondensation.
b
ꢀ
Sample
Acidity
Acidity
TOF p,p /o,p’
+
+
2
(mmol H /g) (mmol H /m )
molar ratio
−
3
EPMO
BPMO
GEPMO
GBPMO
SBA-propyl-SO H
3
1.72
0.93
0.80
0.90
–
1.3 × 10
0.9 × 10
1.1 × 10
1.4 × 10
–
4.6
2.7
17.2
7.6
3.1
3.4
3.5
3.2
−3
−3
−3
12
8.8 10.0
a
7
0 mmol, phenol; 10 mmol, acetone; 70 mg, catalyst; reaction tempera-
◦
ture, 85 C; reaction time, 24 h.
b
TOF is based on mmol of Bisphenol A/mmol of active site.
PMO is the larger specific surface areas and average pore
diameters of the former.
A SBA-15 material functionalized with propylsulfonic
groups was tested for the same reaction by others [12].
The preparation involved the grafting of MPTMS on purely
siliceous SBA-15 followed by oxidation of the thiol group
with H2O2. A TOF of 8.8 was obtained with this material
−3
−3
+
2
(
Table 3). It is worth noting that only two structural iso-
mers of Bisphenol A were formed. No other by-products
such as chroman and trisphenol were detected. For most of
the sulfonic acid-functionalized organosilicas, the ratio of
p,p -Bisphenol A to o,p -Bisphenol A was around 3 that is
substantially lower than the ratio for SBA-propyl-SO3H.
ꢀ
ꢀ
4
. Conclusion
Sulfonic acid-functionalized periodic mesoporous orga-
nosilicas with well-ordered mesoporous structure were syn-
thesized directly by cocondensation of ethane- or benzene-
bridged silsesquioxanes precursors with MPTMS in acidic
medium in the presence of H2O2. The complete oxidation
of –SH to –SO3H was achieved with this in situ oxidation
method. The highest acidity of the mesoporous organosilicas
The catalytic activity of sulfonic acid-functionalized
mesoporous organosilicas also differs with different bridg-
ing organic moieties in the framework. The activity of
GEPMO was higher than that of GBPMO and the same
tendency was observed for organosilicas synthesized by a
direct cocondensation method in acidic medium. One of the
reasons for the observed trend that ethylene-bridged PMO
showed higher catalytic activity than the phenyl-bridged
+
synthesized by this direct method is 1.72 H mmol/g. These
sulfonic acid-functionalized organosilicas are efficient cata-
lysts for the condensation reaction of phenol with acetone to
form Bisphenol A. Ethane-bridged mesoporous organosil-
icas exhibit higher catalytic activity than benzene-bridged
organosilicas.

272
Q. Yang et al. / Journal of Catalysis 228 (2004) 265–272
Acknowledgments
[7] M.C. Burleigh, M.A. Markowitz, M.S. Spector, B.P. Gaber, J. Phys.
Chem. B 105 (2001) 9935.
[
8] M.C. Burleigh, M.A. Markowitz, M.S. Spector, B.P. Gaber, Lang-
muir 17 (2001) 7923.
Financial support of this work was provided by the Na-
tional Science Foundation of China (20303020), National
Basic Research Program of China (2003CB615803), and
Talent Science Program of the Chinese Academy of Sci-
ences.
[9] S. Hamoudi, S. Kaliaguine, Chem. Commun. (2002) 2118.
[10] A. Sayari, Y. Yang, Chem. Commun. (2002) 2582.
11] D. Das, J.F. Lee, S. Cheng, Chem. Commun. (2001) 2178.
12] V. Dufaud, M.E. Davis, J. Am. Chem. Soc. 125 (2003) 9403.
13] I. Díaz, C. Márquez-Alvarez, F. Mohino, J. Pérez-Pariente, E. Sastre,
J. Catal. 193 (2000) 295.
[
[
[
[
[
[
[
14] Q.H. Yang, M.P. Kapoor, S. Inagaki, J. Am. Chem. Soc. 124 (2002)
9694.
References
15] I. Díaz, C. Márquez-Alvarez, F. Mohino, J. Pérez-Pariente, E. Sastre,
J. Catal. 193 (2000) 283.
16] D. Margolese, J.A. Melero, S.C. Christiansen, B.F. Chmelka, G.D.
Stucky, Chem. Mater. 12 (2000) 2448.
17] M.C. Burleigh, M.A. Markowitz, S. Jayasundera, M.S. Spector, C.W.
Thomas, B.P. Gaber, J. Phys. Chem. 107 (2003) 12628.
[1] S. Inagaki, S. Guan, Y. Fukushima, T. Ohsuna, O. Terasaki, J. Am.
Chem. Soc. 121 (1999) 9611.
[2] T. Asefa, M.J. MacLachlan, N. Coombs, G.A. Ozin, Nature 402 (1999)
867.
[
[
3] S. Inagaki, S. Guan, T. Ohsuna, O. Terasaki, Nature 416 (2002) 304.
4] B.J. Melde, B.T. Holland, C.F. Blanford, A. Stein, Chem. Mater. 11
[18] Q. Yang, Y. Li, L. Zhang, J. Yang, J. Liu, C. Li, J. Phys. Chem. B 108
(2004) 7934.
(
1999) 3302.
[19] K.J. Shea, D.A. Loy, O. Webster, J. Am. Chem. Soc. 114 (1992) 6700.
[20] Y. Goto, S. Inagaki, Chem. Commun. (2002) 2410.
[21] J.G.C. Shen, R.G. Herman, K. Klier, J. Phys. Chem. B 106 (2002)
9975.
[
5] C. Yoshina-Ishii, T. Asefa, N. Coombs, M.J.G. MacLachlan, A. Ozin,
Chem. Commun. (1999) 2539.
6] T. Asefa, M. Kruk, M.J. MacLachlan, N. Coombs, H. Grondey, M.
Jaroniec, G.A. Ozin, J. Am. Chem. Soc. 123 (2001) 8520.
[
[22] M.H. Lim, A. Stein, Chem. Mater. 11 (1999) 3285.