Lewis acidity quantification and catalytic activity of Ti, Zr and Al-supported mesoporous silica

Article abstract of DOI:10.1039/C7DT00035A

Water-tolerant supported Lewis acids are actively sought after, in particular to address the challenging direct amidation reaction. To this aim, a versatile and easy synthesis of large pore silica materials with supported Ti-, Al-, Zr-Lewis acids, using acetyl acetonate as a metal-stabilizing agent, was accomplished. The formation of bulk metal oxides was not observed, even at high concentrations of metal species. The Lewis acidity was demonstrated using quantitative and qualitative titration techniques using a series of Hammett indicators, such as butter yellow, phenylazodiphenylphosphine and dicinnamalacetone. The optimal concentration of metals corresponding to the highest Lewis acidity of solids was found to be 4% for Al-SBA-15, 12-15% for Ti-SBA-15 and 7% for Zr-SBA-15 materials. The water-tolerance of the supported metal centers was explored by a pyridine adsorption-FTIR study before and after water addition. The metalated materials were used as water-tolerant heterogeneous catalysts for the amidation of electron-poor and bulky amines, such as substituted anilines and morpholine, obtaining 59-99% yield of the corresponding amides.

Full text of DOI:10.1039/C7DT00035A

View Article Online
View Journal
Dalton
Transactions
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: M. V. Zakharova,
F. Kleitz and F. Fontaine, Dalton Trans., 2017, DOI: 10.1039/C7DT00035A.
This is an Accepted Manuscript, which has been through the
Volume 45 Number
1 7 January 2016 Pages 1–398
Royal Society of Chemistry peer review process and has been
accepted for publication.
Dalton
Transactions
Accepted Manuscripts are published online shortly after
An international journal of inorganic chemistry
www.rsc.org/dalton
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
author guidelines.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the ethical guidelines, outlined
in our author and reviewer resource centre, still apply. In no
event shall the Royal Society of Chemistry be held responsible
for any errors or omissions in this Accepted Manuscript or any
consequences arising from the use of any information it contains.
ISSN 1477-9226
PAPER
Joseph T. Hupp, Omar K. Farha et al.
Efficient extraction of sulfate from water using
framework
a Zr-metal–organic
rsc.li/dalton

Please do not adjust margins
Page 1 of 14
Dalton Transactions
View Article Online
DOI: 10.1039/C7DT00035A
Journal Name
ARTICLE
Lewis Acidity Quantification and Catalytic Activity of Ti, Zr and Al-
Supported Mesoporous Silica
Received 00th January 20xx,
Accepted 00th January 20xx
M. V. Zakharova,a F. Kleitz*b and F.-G. Fontaine*a
DOI: 10.1039/x0xx00000x
Water-tolerant supported Lewis acids are actively sought after, in particular to address the challenging direct amidation
reaction. To this aim, a versatile and easy synthesis of large pore silica materials with supported Ti-, Al-, Zr- Lewis acids,
using acetyl acetonate as metal-stabilizing agent, was accomplished. The formation of bulk metal oxides was not observed,
even at high concentration of metal species. The Lewis acidity was demonstrated using quantitative and qualitative
titration techniques using a series of Hammet indicators, such as butter yellow, phenylazodiphenylphosphine and
dicinnamalacetone. The optimal concentration of metals corresponding to the highest Lewis acidity of solids was found to
be 4% for Al-SBA-15, 12-15% for Ti-SBA-15 and 7% for Zr-SBA-15 materials. The water-tolerance of the supported metal
centers was explored by a pyridine adsorption-FTIR study before and after water addition. The metalated materials were
used as water-tolerant heterogeneous catalysts for the amidation of electron-poor and bulky amines such as substituted
anilines and morpholine obtaining 59-99% yield of the corresponding amides.
www.rsc.org/
Keywords: metalation • mesoporous materials • Lewis acids • amide synthesis • heterogeneous catalysis
high interest in green solvents for catalysis makes the synthesis of
water-tolerant solid Lewis acids a target of great interest.5 Zeolites
are among the most important examples of heterogeneous
Introduction
Lewis acid catalysts are playing a primary role in many industrial
chemical processes. Although not inclusive, the list of organic
transformations and rearrangements catalyzed by Lewis acid
catalysts include notably the Mukaiyama-Aldol,1 the Diels-Alder2
and the Friedel–Crafts3 reactions, which commonly result in
formation of new C-C, C-N and C-O bonds. The typical Lewis acids
used for these applications include soluble complexes of Ti4+, Al3+,
Sn4+, and Zr4+. However, the removal of homogeneous catalysts in
large scale processes can be costly and troublesome and
heterogeneous catalysis presents itself as an alternative of choice.
Although many Lewis acidic materials have been reported, most of
these compounds exhibit significant moisture sensitivity.4
Moreover, conventional Lewis acids require pretreatment in order
to break any Lewis adducts occurring between the active sites and
moisture, which can lead to catalyst degradation. In addition, the
catalysts comprising both Brønsted and Lewis acidic sites,
originating from the aluminum atoms residing in the framework.6 In
the early 1980s, titanium silicalite-1 (TS-1) materials were shown to
exhibit isolated Lewis acid sites in crystalline microporous materials
without the presence of Brønsted acid sites.7 However, these Lewis
acid sites were hardly accessible for chemical transformations, such
as for oxidation, because of the microporosity of the materials. In
order to catalyze reactions with larger substrates, Ti4+ atoms were
also introduced into the framework of 12-membered ring zeolites
(Ti-Beta) and into ordered mesoporous silica matrices (e.g., Ti-
MCM-41).8 However, in some cases, a lower reactivity with respect
to TS-1 was observed suggesting that the location of the Ti sites
and the environment surrounding these sites were influencing the
activity.9
Metal-organic frameworks (MOF) also exhibit catalytically relevant
features similar to zeolites, including large internal surface areas
and uniform pore and cavity sizes.10 Some MOFs having Al11, Cd12,
Cu13, In14, Mn15, Sc16,17 or Cr18 nanoclusters have been shown to be
very active Lewis acid catalysts. However, the low stability of these
materials toward moisture, temperature, and some reactants,
owing to the presence of organic linkers, especially in comparison
to the stability of the covalent Si-O bonds in zeolites, is significantly
limiting their industrial use.19 Nevertheless, in the past few years,
some new synthetic strategies have been developed in order to
overcome the aforementioned drawbacks.20
a. M. Zakharova, Prof. Frédéric-Georges Fontaine
Département de Chimie, Centre de Catalyse et Chimie Verte (C3V)
Université Laval
1045 Avenue de la Médecine, Québec, QC G1V 0A6, Canada
E-mail: frederic.fontaine@chm.ulaval.ca
b. Prof. Freddy Kleitz
Département de Chimie, Centre de Recherche sur les Matériaux Avancés (CERMA)
Université Laval
1045 Avenue de la Médecine, Québec, QC G1V 0A6, Canada
E-mail: freddy.kleitz@chm.ulaval.ca
Electronic
Supplementary
Information
(ESI)
available.
See
DOI: 10.1039/x0xx00000x
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

Please do not adjust margins
Dalton Transactions
Page 2 of 14
ARTICLE
Journal Name
One of the most convenient and cheap supports for Lewis acid
catalysts has been silica-based mesoporous materials21-30 owing to
their high specific surface area and relatively large pore sizes
compared to zeolitic materials and MOFs.25,26 Moreover, materials
synthesized with non-ionic triblock copolymers as templates, e.g.,
SBA-15 (Hexagonal 2-D)31,32 , SBA-16 (Cubic 3-D)31,33,34 and KIT-6
(Cubic 3-D)35, were found to exhibit enhanced stability
(hydrothermal and mechanical), owing to their larger pore wall
thickness compared to ionic surfactant-based MCM-41-type
as a reusable, inexpensive Lewis acid catalyst for the amidation of
View Article Online
substrates such as anilines and α-hydroxycarboxylic acids.
53
DOI: 10.1039/C7DT00035A
Additionally, multiple heterogeneous Bronsted acids were reported
for such purpose.56 In the present study, we aim to develop
efficient solid Lewis acid catalysts for the direct amidation reaction.
For this, we are reporting the synthesis of Ti-, Al-, Zr-SBA-15
materials made by a straightforward post-synthesis metalation
methodology using acetylacetonate metal precursors. A qualitative
and quantitative study of the Lewis acidity of these materials was
performed to fully ascertain the nature and the distribution of the
active sites. The water tolerance of these materials was proven by
pyridine adsorption-FTIR studies comparing their properties with
and without water. Finally, the materials were applied to the Lewis
acid-catalyzed amidation of aniline and morpholine with
undecanoic acid, obtaining high catalytic performance.
mesoporous silica36-38
.
Only few approaches were reported in order to introduce metal
Lewis acidic character to mesoporous solid supports. Among them,
the incorporation of metal precursors into the framework of
mesoporous silica,39 the synthesis of hybrid periodically-ordered
mesoporous organosilica (PMO) materials40 and direct surface
grafting41-43 resulted in highly catalytically active solid materials.
PMO materials contain organic N, O, S- moieties that are
incorporated into the mesoporous framework while metal Lewis
acidic centers are anchored to the surface through covalent
interactions. In this way, Polarz and coworkers performed the
synthesis of a PMO containing AlIII centers for the asymmetric
carbonyl-ene reaction.44 Chuah reported the synthesis of Zr-SBA-15
with Zr4+ ions incorporated into a mesoporous framework, which
confers to the material strong Lewis acidity, as well as
incorporating weak Brønsted acidic sites, essential for the Prins
reaction between pinene and paraformaldehyde.39 Recently, the
Tilley45 and Kleitz groups studied the co-condensation46 and post-
synthesis grafting47 of Ti4+ organometallic precursors in large pore
SBA-15 silica. Using a similar strategy, Hara successfully used these
Ti-SBA-15 materials for the Mukaiyama-aldol condensation of
benzaldehyde with 1-trimethylsilyloxy-cyclohexene in water.48
However, despite the aforementioned progress, there is still
significant lack of diversity and in-depth study of solid-supported
Lewis acids capable to catalyze various transformations in the
presence of moisture, which slows down their development and
application.
Experimental section
Characterization techniques
Low-angle X-ray diffraction (XRD) patterns were collected on a
Rigaku Multiflex diffractometer using Cu Kα radiation (λ = 0.1541
nm). The XRD scanning was performed at 30 kV and 40 mA (1.2
kW), with steps of 0.01 and an acquisition time of 2 s. The
reference patterns of the different single metal oxides were
obtained from the Powder Diffraction File 2 (PDF-2) database
licensed by the International Center for Diffraction Data (ICDD). The
nitrogen adsorption-desorption isotherms were determined at -196
°C using an Autosorb-1 sorption analyzer. Prior to analysis, the
samples were outgassed at 200 °C (for non-passivated materials)
and at 80 °C (for passivated materials) for 12 h. The pore size
distribution was obtained by the non-local density functional
theory (NLDFT) method and calculated using the Autosorb-1 1.55
software, supplied by Quantachrome Instruments, USA. The NLDFT
kernel selected considers sorption of N2 on silica at -196 °C
assuming a cylindrical pore geometry and the model of equilibrium
isotherm based on the desorption branch and compared to value
obtained from adsorption branch (using the model of metastable
adsorption). Attenuated total reflectance infrared (ATR-IR) spectra
were recorded using a Nicolet Magna 850 Fourier transform
spectrometer equipped with a liquid nitrogen cooled narrow band
MCT detector. Each spectrum was obtained from the acquisition of
128 scans at 4 cm-1 resolution from 4000 to 700 cm-1 using a Happ–
Genzel apodization. Diffuse-reflectance UV–vis spectra were
recorded using a Varian Cary 500 spectrophotometer equipped
with a Praying Mantis accessory. A Spectralon reflectance standard
was used as a reference. X-ray photoelectron spectroscopy (XPS)
In particular, the direct amidation catalyzed by heterogeneous
Lewis acids still represents an important challenge since many
pharmaceutically and biologically important compounds are
constituted of amide bonds as building blocks.49-53 The catalytic
synthesis of amides from readily available starting materials is a
priority area for the pharmaceutical industry.49,53 There have been
a limited number of heterogeneous Lewis acid catalysts studied for
direct amidation of electron-poor or hindered amines such as
aniline and morpholine.53 Sasaki and Sugi reported calcium
containing mesoporous aluminosilicate molecular sieves, having
both Lewis and Bronsted acidic properties, which show interesting
activity in the catalytic amidation of palmitic acid with N-
hexadecylamine.54 Sarvari and Sharghi described the treatment of
amines with formic acid in the presence of ZnO under solvent-free
conditions to generate the corresponding formamides in excellent
yields.55 Shimizu also reported a solid niobium oxide capable to act
spectra were collected on
a
Kratos Axis-Ultra electron
spectrometer (UK) using a monochromatic Al Kα X-ray source (Al k
= 1486.6 eV) at a power of 300W and operated at a base pressure
of 10-10 Torr. Charge compensation was performed using a low-
energy electron beam perpendicular to the surface of the samples.
Survey spectra used for determining the elemental composition
were collected at pass energy of 160 eV. SEM images and EDX
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
Page 3 of 14
Dalton Transactions
Journal Name
ARTICLE
spectra were recorded using a JEOL JSM-840 instrument with an
acceleration voltage of 15 kV. The samples were first dispersed on
an aluminum stub and coated with Au/Pd film before analysis.
Spectra were recorded using backscattered electrons (BSE)
technique to increase the contrast between the transition metal
oxide particles and the external surface of the metalated SBA-15.
High-resolution TEM (HR-TEM) and EDX analyses were carried out
on a Cs-corrected Titan G2 ETEM at an accelerating voltage of 300
kV. EDX elemental mapping images were obtained from a square
area of 15*15 nm (100*100 pixels) with an acquisition time of 1 s.
For TEM/EDX imaging, powder samples were dispersed in acetone
and a few drops of the solution were placed on a holey carbon film
coated 300 mesh copper grid. 13C cross-polarization (CP/MAS), 29Si
and 27Al magic-angle-spinning (MAS) nuclear magnetic resonance
(NMR) analyses were carried out on a Bruker Advance 300 MHz
spectrometer (Bruker Biospin Ltd, Milton, Canada) at 75.4 MHz for
13C, 59.6 MHz for 29Si and 78.172 MHz for 27Al nuclei
correspondingly. 29Si MAS NMR spectra were recorded with a spin
echo sequence to avoid instrument background with a recycle
delay of 30 seconds in a 4 mm rotor spinning at 10 kHz. 13C CP/MAS
NMR spectra were recorded with a 4 mm MAS probe with a
spinning rate of 10 kHz and contact time of 1 ms. Chemical shifts
were referenced to tetramethylsilane (TMS, δ= 0.0 ppm) for 29Si
and adamantane (δ= 28.6 ppm) for 13C NMR. Liquid NMR spectra
were recorded on a Varian Inova NMR AS400 spectrometer at
400.00 MHz (1H NMR).
aluminum iso-propoxide) and acetyl acetone (AA) (VAieAw/MArtic=le 3O.n1lin5e)
DOI: 10.1039/C7DT00035A
was slowly added to the mixture at 15 °C and then stirred for 2 h.
After filtration and washing with ethanol, the material was calcined
at 550 °C for 5 h in air in order to immobilize the metal species on
the silica surface. The resulting Ti4+, Zr4+ and Al3+ deposited
mesoporous silica samples with different metal contents were
denoted as M-x-SBA-15 (M=Ti, Zr, Al; x = metal molar % obtained
from XPS surface analysis). The silica yield is assumed to be 100 %.
For comparison purposes, the materials were compared to bulk
anatase TiO2, ZrO2 (Alfa Products) and ɣ-Al2O3 (Sigma-Aldrich)
used without additional purification.
Passivation of SBA-15 and M-SBA-15. Passivation of surface silanol
groups was performed using tetramethyldisilazane (TMDS) as a
silylating agent.57 In a typical protocol, 1 g of SBA-15 material
preliminary degassed at 160 °C in a vacuum oven overnight was
dispersed in 50 ml of dry hexanes and 2 ml of TMDS was added
dropwise under vigorous stirring. The mixture was left stirring for
24 h at room temperature. The excess TMDS was removed by
Soxhlet extraction for 12 h at 60 °C using dichloromethane as a
solvent. The obtained passivated materials were then dried in a 60
°C oven for 12 h.
Investigation of the Lewis acidity
Titration of solids with Hammet indicators. The titration with
Hammet indicators was performed accordingly to protocols
described elsewhere.58,59 Color tests were made by transferring
about 0.1 g of dried and powdered solid to a test-tube, adding 3-5
ml of freshly distilled benzene, followed by the addition of a 0.1 %
solution of the indicator in benzene (three drops). From the results
of such tests, it was easy to decide whether the solid under study
was basic to all indicators, acid to all indicators, or had an H0 value
lying between two adjacent indicators. The samples were dried and
stored in a screw-cap bottle in a desiccator prior to the colorimetric
tests. The effect of water adsorption was to either decrease the
color intensity of the absorbed indicators or to cause a shift to
lower acid strengths. By carrying out parallel tests inside and
outside a dry box, water adsorbed during a single transfer of dried
sample to the test-tube had a negligible effect on acid strength.
Synthesis of SBA-15 material. Mesoporous silica SBA-15 was
synthesized using amphiphilic block copolymer P123 (Sigma-
Aldrich, MW = 5800) as a structure-directing agent and tetraethyl
orthosilicate (TEOS) as a silica source.46 In a typical synthesis, 10 g
of P123 was dissolved in a mixed solution of distilled water (75 g)
and HCl (2 M, 250 ml) at 35 °C during 2 hours. TEOS (21.5 g) was
then added into the clear solution and the mixture was stirred at 35
°C for 20 h, followed by heating the solution at 100 °C for 24 h
under static conditions. The resulting white precipitate was stirred
in water (100 ml) containing few drops of concentrated HCl for 30
minutes, filtered off and washed with water (100 ml). Calcination of
the resulting silica at 550 °C for 5 h in air resulted in mesoporous
silica SBA-15.
Pyridine Adsorption FT-IR experiments. The adsorption tests were
performed on 50 mg of solid materials freshly degassed at 160 °C
for 24 h which were dispersed in 3 ml of a 5 % pyridine solution in
dry hexane. After stirring the solid suspension for one hour, the
solvent was removed under reduced pressure and the solids were
continuously outgassed first at 100 °C for 1 h and then at room
temperature for 16 h. As a final step, the white powders were
analyzed by FT-IR spectroscopy.
Metalation of SBA-15. Ti-, Al- and Zr-SBA-15 materials with
different molar ratios were synthesized using a post-grafting
method as reported earlier46,47 with some modifications. In a
typical synthesis, 6 g of P123 was dissolved in a mixed solution of
distilled water (114 g) and HCl (37 wt%, 3.5 ml) at 35 °C for 2 hours.
TEOS (21.5 g) was then added into the clear solution and the
mixture was stirred at 35 °C for 20 h, followed by heating at 100 °C
for 24
h under static conditions. The resulting suspension
containing precipitated SBA-15 (5 g) was added to a mixture of
distilled water (145 g) and ethanol (15 g) at room temperature.
After the pH of the solution was adjusted to 10.0 with diluted
ammonia, a mixture of ethanol (20 g), of the respective metal
precursor (titanium iso-propoxide, zirconium n-butoxide or
Quantitative titration. The quantitative titration technique
developed by Johnson59 was modified so that the indicators could
be added to portions of the metalated catalyst suspension after it
had been equilibrated with n-butylamine.60 Prior to the titration
tests, 0.1 wt% solutions of the Hammet indicators in dry benzene
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
Dalton Transactions
Page 4 of 14
ARTICLE
Journal Name
were prepared and used the same day. About 600 mg of freshly
calcined metalated materials were transferred to a 150 °C vacuum
oven and dried for 24 h. About 200 mg of sample was transferred
into dried 8 ml vials and 6 ml of dry benzene was added to each of
the samples. Different volumes of a 0.1 M solution of n-butylamine
in benzene were added to these samples (0.1, 0.2, 0.3 and 0.4
mmoles of n-butylamine per gram of powder). The tightly capped
samples were then stirred vigorously at room temperature for 4 h
(increasing the time to 12 h did not influence the titration test
results). Each of the suspensions were separated in three different
dry 8 ml vials (2 ml of a suspension containing approximately 67 mg
of the catalyst) and 4 drops of one Hammet indicator solution were
added, repeating the process for each indicator. The quantification
of the number of acidic sites was done by considering the amount
of n-butylamine required before no color change was observed
with the Hammet indicator.
quantity was varied from 1 to 20 mol% in order to obtain the
DOI: 10.1039/C7DT00035A
materials with high metal loading while preserving mesoporosity.
View Article Online
First of all, the synthesized materials were analyzed using nitrogen
physisorption at -196 °C (Figure 1). Typical type IV isotherms with
H1 hysteresis loops were identified for all materials with the
exception of Zr-7%-SBA-15, where the uniformity of the mesopores
was significantly lost upon the introduction of 10 mol% of
zirconium-alkoxide precursors (Figure 1C). In the latter case, a
broad pore size distribution was observed with a maximum at 9.3
nm (Table 1). Similar observations were done by other research
groups when attempting to graft zirconium to SBA-15 materials,
which was attributed to mesopore blocking caused by the
formation of zirconia (ZrO2 particles) inside the pores at higher
loadings (above 10 mol%).61-65,66
For the Al-SBA-15 materials (Figure 1A) one can observe the onset
of the capillary condensation step shifted to lower relative
pressures when the concentration of the aluminum grafted on the
surface increases. Similar effect was observed for Ti-SBA-15 (Figure
1B) and Zr-SBA-15 (Figure 1C) materials, but in the latter two
classes of materials this effect was significantly less pronounced
than in the case of the Al-containing mesoporous materials. In the
case of low Ti, Al and Zr loadings, a higher volume of nitrogen was
adsorbed compared to that of the parent SBA-15 (Table 1). Such
phenomenon was reported for the impregnation of metals in a
SBA-15 solid matrix, where an increase of up to 15 % of the total
volume adsorbed and of the BET surface area were observed when
compared to starting SBA-15 material.68 Block polymer templated
ordered mesoporous materials, such as SBA-15 silica, usually
contain micropores/small mesopores, or at least a very rough
channel surface, in their framework walls.32 Loading the materials
with Ti-, Al- and Zr-alkoxides can alter this microporous corona in a
difficult-to-control manner and lead to some change in the sorption
data at low metal loading. In particular, an increase in specific
surface area and in the volume adsorbed seems possible, if
restructuring of the microporous section of the walls takes place.68
Catalytic amidation test. Passivated solid catalysts were degassed
at 70 °C under reduced pressure in a vacuum oven for 24 h prior to
the catalytic tests. In a typical experiment, the carboxylic acid (1
mmol), the amine (1 mmol) in toluene (2.5 mL) and the metalated
SBA-15 (50 mg) were added to a round-bottom flask equipped with
a reflux condenser and a magnetic stirrer. The reaction mixture was
heated to reflux under an N2 atmosphere and stirred for 48 h. After
completion of the reaction, dichloromethane (25 ml) was added to
the mixture, and the solid catalyst was separated by centrifugation
followed by one cycle of washing with 25 ml of dichloromethane
after which the centrifugation was repeated. After a second
centrifugation, the organic fractions were combined and acidified
with 5% aqueous HCl. The final product was extracted from the
dichloromethane organic phase, dried over MgSO4 and
concentrated under a rotary evaporator. The yield of the product
was determined by using 1H NMR spectroscopy with dry 1,3,5-
trimethoxybenzene as an internal standard.
Results and discussion
X-ray photoelectron spectroscopy was used to probe the metal
concentration on the surface.46,47 As presented in Table 1, only a
fraction of the initial metal-alkoxide concentration (4-20 mol%) can
be grafted on the surface. Whereas the maximum concentration of
metals in Al- and Ti-containing materials (respectively, 20 and 15
mol%) were obtained when the highest concentration of metallic
starting materials was used (respectively, 50 and 40 mol%), a
maximum loading of 7 mol% was observed for the Zr materials
when a 10 mol% of zirconium alkoxide was used. A higher loading
of 40 mol% of the zirconium starting reagent only led to 6% Zr
incorporation, presumably caused by the formation of bulk
zirconium oxide. The latter material was labeled as Zr-6%-SBA-15*.
It is worth noting that the grafting of a 7 mol% concentration on
silica materials without formation of crystalline zirconia was only
observed once before.67
Materials characterization
Al-, Ti- and Zr-metalated materials were synthesized according to a
modified post-synthesis protocol,43,44,47 using acetyl acetonate as a
metal-stabilizing agent to prevent the formation of metal oxide
clusters in the pore channels or on the external surface of the
solids. The presence of this ligand has been shown to reduce the
rate of M-O-M formation while increasing the generation of M-O-Si
linkages, thus favoring the formation of single metal sites and
avoiding the generation of bulk metal oxides. Therefore, the use of
such Ti, Al, and Zr precursors chemically modified with organic
ligands resulted in high metal dispersion on the silica surface.46,47
The Ti4+, Zr4+ and Al3+ deposited mesoporous silica samples with
different metal contents were denoted as M-x-SBA-15 (M=Ti, Zr, Al;
x = metal molar % obtained from XPS surface analysis). The metal
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
Page 5 of 14
Dalton Transactions
Journal Name
ARTICLE
Table 1. Physicochemical properties derived from N2 sorption
measurements at -196 °C and XPS analysis performed on the
different Ti-, Al- and Zr-SBA-15 materials.
View Article Online
DOI: 10.1039/C7DT00035A
a
b
c
d
e
M/Siinitial
M/Sifinal
SBET
NLDFTads
NLDFTdes
Vt
Sample
SBA-15
[mol%]
0
[mol%]
0
[m2/g]
814
[nm]
8.1
[nm]
7.6
[cm3/g]
1.0
Ti-SBA-15
777
1
2
3
10
30
40
7
8.8
8.1
8.1
9.1
8.1
8.1
1.4
0.7
0.8
12
15
408
472
Al-SBA-15
721
4
5
6
4
3
4
9.3
9
9.7
9.2
7
1.4
1.4
0.5
10
50
671
Figure 1. N2 adsorption–desorption isotherms measured at 77.4 K
(-196 °C) for Al- (A), Ti- (B), Zr-SBA-15 (C).
20
403
7.3
Zr-SBA-15
641
7
8
4
5
2
5
7
6
9.4
9.4
9.0
8.1
9.7
1.1
1.6
824
9.7/ 10.4
9.3broad
8.1
Wide-angle powder X-ray diffractograms of metalated SBA-15 silica
as well as the reference metal oxides are shown in Figure S2 (see
Supporting Information). In all cases, except for Zr-6%-SBA-15*, no
crystalline TiO2, Al2O3 or ZrO2 phase was identified on the surface
indicating that either the metal layers coated on the pore walls
were amorphous in nature and did not crystallize even after
calcination at 550 °C or metallic particles were too small to be
detected.Erreur ! Signet non défini. This suggests that the metal
species are predominantly inside the pores of SBA-15 restricting
the growth of crystals. Zr-6%-SBA-15* material exhibits broad
signals at 30-33° and 50-60° that were attributed to the presence
of ZrO2 (Figure S2). Indeed, the SEM images of Zr-6%-SBA-15*
materials reveal ZrO2 particles outside the mesopores with an
estimated size of 15 microns (Figure 2C). The elemental
composition of zirconia particles was confirmed by EDX analysis
and compared to the amorphous phase of Zr-grafted SBA-15
fragment (Figure 2D, E). The EDX spectrum of the particles
appearing white (Figure 2C, ZrO2) consists predominantly of those
expected for ZrO2, while spectra of the amorphous domain (Figure
2C, Zr-SiO2) demonstrates three major signals for silica, oxygen and
zirconium with a corresponding Si/Zr intensity of 6%. Besides Zr-
6%-SBA-15*, the characteristic thread-like morphology of SBA-15
was observed for all materials and no crystalline domains were
detected (Figure 2A, B).
9
10
40
752
1.3
10*
589
0.73
[a] Ti/Si molar ratio obtained by XPS technique; [b] SBET , apparent BET specific surface
areas deduced from the isotherm analyses in the relative pressure range from 0.05 to
0.20; [c] NLDFTads , primary mesopore diameter estimated using the NLDFT method.
The model used for the NLDFT evaluation was N2 adsorbed on silica with cylindrical
pores assuming the adsorption branch (model of metastable adsorption); [d] NLDFTdes
,
primary mesopore diameter estimated using the NLDFT method. The model used for
NLDFT evaluation was N2 adsorbed on silica with cylindrical pores using the desorption
branch (equilibrium sorption model); [e] Vt , total pore volume taken at relative
pressure P/P0=0.95.
The grafting of titanium to the surface increases the intensity ratio
between the higher order reflections (110) and (200) and the (100)
reflection. This phenomenon was documented earlier for rare-
earth impregnated materials and attributed to the flattening of the
electron density distribution inside the pores of the materials with
low degree of metal surface.68
The low angle X-ray diffractograms of the titanated SBA-15
materials are shown in Figure S1 (see Supporting Information). The
diffractograms show three diffraction peaks associated with the
(100), (110) and (200) reflections at 0.91, 1.4 and 1.8° 2θ, indicating
retention of the typical two-dimensional (2-D) hexagonal
(symmetry group p6mm) structure of SBA-15.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 5
Please do not adjust margins

Please do not adjust margins
Dalton Transactions
Page 6 of 14
ARTICLE
Journal Name
The fact that Ti- and Al- metal oxide particles did not crystallize
even at higher calcination temperatures suggests the presence of
strong interactions of the grafted metals with the silica surface.61,64
The presence of adsorption peaks at 940-990 cm-1 for Ti-SBA-15
materials using Fourier transform infrared (FTIR) spectroscopy of
titanium-coated SBA-15 samples (Figure 3) indicates the existence
of Si–O–Ti linkages, which are absent in the reference spectrum of
bulk titania. Analogous observations were made for Al- and Zr-SBA-
15 materials with corresponding M-O-Si stretching bands at 966
and 951 cm-1, respectively (Figures S3-S4).
View Article Online
DOI: 10.1039/C7DT00035A
Figure 3. FTIR spectra of Ti-SBA-15 materials with different Ti
concentrations.
However, when the titanium concentration increases up to 15%, a
45 nm red shift of the adsorption band to the 310-318 nm region
was observed, probably due to the formation of some Ti–O–Ti
bonds. This phenomenon was previously observed and attributed
to formation of TiO2 units in bulk amorphous titania.46,47 Indeed,
the reference bulk titania sample showed absorption bands at 250
and 280 nm caused by O2- to Ti4+ charge-transfer in 4- and 6-
coordinated TiO2 species correspondingly.46,47
Figure 2. SEM images of Ti-15%-SBA-15 material under x1000 (A)
and x100 (B) folds magnification; SEM image of Zr-6%-SBA-15*
under x1000 (C) fold magnification and EDX spectra Zr-6%-SBA-15*
containing zirconia crystalline region (D) and amorphous region (E).
Figure. 4. UV-vis DR spectra of Ti-SBA-15 samples with different Ti
concentrations.
Inspection of the UV-visible diffuse reflectance spectra (UV-vis DRS)
of the titanium-coated SBA-15 samples gives a clear indication of
the coordination environment of the metal centers (Figure 4). The
materials having a low Ti loading on the material surface (such as
Ti-7%-SBA-15) have a predominant signal between 250 and 260
nm, suggesting that titanium is essentially dispersed on the silica
surface framework as TiO44- tetrahedra.46,47
Solid state 27Al MAS NMR was used as a complementary method
for the determination of the coordination environment of the
aluminum centers in the Al-SBA-15 materials. Similarly to Ti-SBA-
15, both signals for the tetra- and hexa-coordinated metal species
were observed with corresponding chemical shifts of 0 and 50-55
ppm.69 A majority of tetra-coordinated centers are observed in low
Al loadings, such as in Al-3%-SBA-15, whereas equal distributions of
tetra- and hexacoordinated environments, with respective shifts of
0 and 51.3 ppm, were observed in Al-20%-SBA-15 (Figures S5-S7).
6 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
Page 7 of 14
Dalton Transactions
Journal Name
ARTICLE
The high resolution transmission electron microscopy (TEM)
analyses of Ti-SBA-15 materials are depicted in Figure 5A-F. These
confirm the preservation of ordered mesopores after metalation.
Also, no crystalline metal oxide was detected after the increase of
titanium in the pores from 1 to 15 mol%. Energy-dispersive X-ray
spectroscopy mapping reveals an even distribution of silicon,
oxygen and titanium atoms as well as the gradual increase of
titanium concentration without the formation of isolated domains.
As it has been shown, using acetylacetonate as a stabilizing agent
allows the successful grafting of Ti, Al and Zr on the surface of SBA-
15 materials without formation of separated crystalline metal oxide
domains, with the exception of the higher loadings of Zr.
appropriate series of indicators, the extrapolated pH scale can be
DOI: 10.1039/C7DT00035A
given by Ho which is the Hammett acidity function (see Supporting
View Article Online
Information for detailed information). Traditional methods of
titration using Hammett indicators are widely used for measuring
the acid strength of solid acids, superacids and ionic liquids.61
Corma and Fornes used the Benesi method to quantify the amount
of acidic centers as well as their strength in zeolites.62 The
mechanism of this titration consists in the interaction of a basic
Hammet indicator (B) molecule with the surface Bronsted acidic
sites (HA) or Lewis acidic sites (LA) with subsequent formation of
the protonation product with the conjugated base (HB+ + A-) or of a
Lewis pair adduct (LA-B), respectively. These products will be
referred as the acidic forms of the Hammet indicators. Since these
Hammet indicators are chromophores, such transformation is
accompanied by a dramatic color change of the solution due to a
significant reorganization of the electronic structure. The colors of
the acidic and basic forms of the Hammet indicators used in the
present study, as well as their pKa values, are presented in Table 2.
There is very little known about the acidity of metalated
mesoporous materials. Xiao synthesized SiO42−/ZrO2 supported
MCM-41 materials, which were later defined as solid superacids
with H0 values around −12.5, as determined using 2,4-
dinitrotoluene as a Hammet indicator.72 A pyridine adsorption-FT-IR
study demonstrated these sites were Lewis acidic. Another
interesting result was obtained by Antonelli and coworkers who
developed
a methodology for the synthesis of mesoporous
materials containing Ti, Nb and Ta oxides.73 The titration methods
demonstrated that sulfated mesoporous Nb samples exhibited very
strong acidity with H0 ≤ -8.2. In these materials, pyridine adsorption
FT-IR analysis demonstrated that both Lewis and Bronsted acidic
centers were present in a 50:50 proportion.73
Table 2. Hammet indicators used in the study, colors of the
corresponding acidic and basic forms and their pKa values.
Figure 5. High resolution transmission electron microscopy spectra of Ti-SBA-
15, where Ti 1% (A, B), Ti 7% (C, D), Ti 15% (E, F) and energy-dispersive X-ray
spectroscopy data of Ti-SBA-15.
The results of the titration of the Ti-, Al-, Zr-SBA-15 materials are
presented in Table 3. It should be noted that the bulk metal oxides
TiO2, ZrO2, Al2O3 and SBA-15, (Table 3, entries 1-4) did not induce
color change. These results clearly demonstrate that grafting metal
sites on the surface of SBA-15 material induces a very strong
increase in acidity characterized by the change of color of the
dicinnamalacetone indicator, suggesting a Hammet constant value
lower than -3. Al-3%-SBA-15 (entry 5), Al-20%-SBA-15 (entry 7), Ti-
4%-SBA-15 (entry 9), Ti-7%-SBA-15 (entry 10), Zr-2%-SBA-15 (entry
13) and Zr-6%-SBA-15* (entry 16) materials were able to partially
Surface acidity tests
In order to have a better insight into the surface acidity coming
from the metal sites, colorimetric tests using various Hammet
indicators were carried out. In order to apply the non-aqueous n-
butylamine titration technique introduced by Benesi,60 it has to be
accepted that the pH scale used to determine the acid strength in
dilute aqueous media can be extrapolated to very strong acidic
media with corresponding negative values of pH. By the use of an
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 7
Please do not adjust margins

Please do not adjust margins
Dalton Transactions
Page 8 of 14
ARTICLE
Journal Name
change the color of dicinnamalacetone indicator; their Hammet
constant was thus estimated to be within the range of [-1.5 - -3]
units.
majority of Lewis acidic centers compared to the Bronsted sites,
DOI: 10.1039/C7DT00035A
even in the presence of water. The Zr-SBA-15 material
demonstrated the strongest water-tolerant character, whereas the
Ti- and Zr-SBA-15 materials produced small amount of Bronsted
acidic centers upon the introduction of water into the system.
View Article Online
The optimal concentration of metal sites on the surface was found
to be different according to the nature of the metal, as
demonstrated by the color change of the Hammet indcator. It was
shown that the optimal acidity was obtained when the materials
comprised of 4% of Al, 12-15% of Ti or 5-7% of Zr. In the case of Al-
SBA-15, an increase in the metal concentration did not have a
significant influence on the acidity. In order to elucidate whether
surface silanol groups of the silica support have an effect on the
acidity of the metalated materials, passivated solids with optimal
metal concentration were synthesized using tetramethyldisilazane
(TMDS) as a protecting group57 and their acidity was tested. After
passivation of the surface silanol groups, the materials were able to
produce a change of the color of all indicators, indicating that the
surface metal centers are responsible for acidity (entries 17-21).
Figure 6. FT-IR spectra for pyridine adsorbed on Ti-, Al-, Zr-SBA-15 materials
Table 3. Results of titration of Ti-, Al-, Zr-SBA-15 materials with
before and after water addition.
Hammet indicators.
Once the Lewis acid character of the metalated solid was
confirmed, a quantitative n-butylamine titration was performed. In
Table 4, the amount of acidic sites for the selected materials is
reported, which is determined by the amount of n-butylamine
needed to prevent a color change of a selected Hammet indicator.
Surface areas measured using the Brunauer-Emmett-Teller method
(SBET), as discussed earlier, allow the conversion of surface acid
concentrations from a unit weight (mmol/g) to a unit surface
(mmol/m2) basis. After comparing Lewis acidity of the obtained
materials with initial metal loading, it becomes obvious that the
Lewis acidity of the solid materials is not a function of the metal
loading, but rather of the metal nature. Indeed, Al-4%-SBA-15 has a
similar concentration of highly Lewis acid sites (pka ≤ -3) than Ti-
15%-SBA-15 (3.0 vs 3.8 mmol/m2) even if the metal loading in the
latter material is four times higher. In the case of the Zr-7%-SBA-15,
even if the concentration of acidic sites is the lowest of all
materials, most of these sites are highly acidic, indicated by similar
concentration of sites at pka ≤+3.3 and pka ≤-3 (1.3 vs 1.1
mmol/m2).
It is possible to distinguish between Lewis or Bronsted acidities by
looking at the vibrational perturbations when a basic molecule
(such as ammonia, pyridine or piperidine) is adsorbed on a solid
surface, being a complementary tool to titration.74 When pyridine
interacts with surface Bronsted sites, the presence of the
pyridinium species is evidenced by adsorption bands at 1540 and
1640 cm-1, while the observation of bands at 1632-1580 and 1455-
1438 cm-1 are attributed to pyridine strongly adsorbed on Lewis
acidic centers.74 Deviations of several reciprocal centimeters can be
observed according to the strength of the surface acidic centers.
The water tolerance of the materials was tested by the addition of
equimolar amounts of water. Figure 6 illustrates the spectra of
pyridine adsorbed on the surface of Ti-, Al- and Zr-SBA-15 with
variable concentrations. All the materials exhibit a significant
8 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
Page 9 of 14
Dalton Transactions
Journal Name
Table 4. Acidity of Al-, Ti-, Zr-SBA-15 materials
ARTICLE
Table 5. Catalytic amidation of aniline catalyzed by metalated SBA-
View Article Online
DOI: 10.1039/C7DT00035A
15 materials.
Sites with pka
Sites with pka
Sites with pka
≤+1.5
≤+3.3
SBET
≤-3
Yield of amide
Material
SBA-15
TONa
[m2/g]
Entry
Solid catalyst
[mmol/m2]
[mmol/m2]
(x 10-4
[mmol/m2]
[mmol/
[mmol/
g]
[mmol/
g]
[%]
1
g]
(x 10-4
)
)
(x 10-4
)
1
2
3
4
5
6
7
8
9
-
-
-
841
671
0
0
0
0
0
0
SBA-15
40
9
Al-4%-
0.4
0.25
0.3
5.5
0.3
4.0
0.2
3.0
SBA-15-TMDS
Al-4%-SBA-15
-
SBA-15
62
61
38
99
26
76
31
-
Ti-12%-
SBA-15
408
472
752
6.1
6.6
1.3
0.2
0.3
0.1
4.7
6.4
1.2
0.1
0.2
0.1
2.5
3.8
1.1
Al-4%-SBA-15-TMDS
Ti-12%-SBA-15
Ti-12%-SBA-15-TMDS
Zr-7%-SBA-15
30
-
Ti-15%-
SBA-15
Zr-7%-
52
-
0.1
SBA-15
Zr-7%-SBA-15-TMDS
Reaction conditions: aniline (96 mg, 1 mmol), undecanoic acid (184 mg, 1 mmol),
solid catalyst (50 mg), dry toluene (3 ml), 110 °C, 48 h. a. TON is defined as the ratio
of moles of product to moles of metal, normalized to the mass of the catalyst used
in the reaction.
Catalytic amidation
The materials synthesized were tested as Lewis acid catalysts for
the amidation of aniline with undecanoic acid. Conventionally,
amides are synthesized from amines and activated carboxylic acid
derivatives, such as carboxylic acid anhydrides or acyl chlorides, or
through activation of a carboxylic acid with a stoichiometric
amount of a condensation agent.52,53 Therefore, the conventional
methods suffer from the production of by-products. As such, it is
generally accepted that the catalytic synthesis of amides from
readily available starting materials is a priority area for the
pharmaceutical industry.49,53 Boron-75,76 or transition metal-based77
Lewis acidic homogenous catalysts have demonstrated several
drawbacks such as water sensitivity, reduced activity by strong
coordination of the basic functional groups, and difficulty in the
removal of the catalyst. Some heterogeneous catalysts have been
reported to effect the direct amidation, but these results were
mainly limited to the N-formylation52,78,79 or N-acetylation52,80 of
amines53 and some of the systems require an excess of reagent.81,82
Without catalyst, the reaction does not proceed readily and only
1% of amide was obtained (entry 1). Quite interestingly, it was
observed that pristine SBA-15 could provide the desired amide in
40% yield (entry 2). The ability of surface silanol groups to catalyze
the amidation reaction was previously observed,53 but the yield of
the reaction is not constant and depends on the quality of the
silica. The passivation of SBA-15 greatly reduces the catalytic
activity, providing only 9% of the desired product under similar
conditions (entry 3). The activity of the non-passivated and
passivated materials was thus verified to compare the influence of
the silanol groups on the activity. All materials were shown to
catalyze the reaction, but Ti-12%-SBA-15-TMDS exhibited the
highest catalytic activity with almost quantitative conversion (entry
7). The Zr-7%-SBA-15-TMDS material also exhibited significant
catalytic activity with an isolated yield of 76%. Interestingly, lower
yields were obtained for both the Ti- and the Zr-based non-
passivated materials, obtaining 38 and 26% yields, respectively,
suggesting that the presence of the silanol groups tends to reduce
the influence of the Lewis acidity. It is possible that hydrogen
bonding provided by the silanol groups on SBA-15 could limit the
interaction of the carboxylic acid with the active metal centers or
that the hydrophobic environment on the passivated materials
would lead to a better exclusion of the water from the pores, which
would lead to higher yields. However, no significant difference in
isolated yields was observed when Al-4%-SBA-15 and Al-4%-SBA-
15-TMDS materials were used (entries 4-5), giving 61-62% of the
amide with both catalysts. Such observation is supported by the
pyridine adsorption-FTIR experiments discussed earlier (Figure 6)
Aniline was chosen as a test-substrate for the direct amidation. The
poor nucleophilicity of the nitrogen atom tends to lead to lower
reactivity and requires a stronger activation of the carboxylic group
for the catalysis to occur.53 The results are presented in Table 5:
O
toluene
reflux
48 h
NH2
HN
O
HO
H2O
+
+
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 9
Please do not adjust margins

Please do not adjust margins
Dalton Transactions
Page 10 of 14
ARTICLE
Journal Name
and attributed to higher sensitivity of Al to water even after the
passivation while Ti and Zr present stronger water tolerant Lewis
acidic character and are thus less affected by the presence of
water. Nevertheless, it should be noted that using wet solvents
decreases slightly the yields observed in all cases.
View Article Online
DOI: 10.1039/C7DT00035A
Conclusions
In conclusion, a versatile and easy synthesis of Ti-, Al-, Zr-supported
solid Lewis acids using acetyl acetonate as metal-stabilizing agent
was demonstrated. It was shown that in most cases, no bulk metal
oxide was formed during synthesis and that the metal distribution
on the surface was achieved, even with 20 mol% of aluminum
grafted on the surface. The Lewis acidity was explicitly
substantiated by titration techniques with a series of Hammet
indicators such as butter yellow, phenylazodiphenylphosphine,
dicinnamalacetone. The water-tolerance of the supported metal
centers was explored by means of pyridine adsorption-FTIR studies
and compared before and after water addition. The optimal
concentration of metal species, providing the highest acidity, was
identified and the dependence on the nature of the metal was
shown. We demonstrated that metal species appended to the solid
support through surface silanol groups are responsible for the
strong Lewis acidity. We believe that such in-depth study provides
an easy and systematic model of Lewis acidity characterization,
which could be easily applicable to various solid materials. Finally,
the metalated materials were shown to exhibit some water
tolerance for amidation of aromatic and bulky amines such as
substituted anilines and morpholine. Although Ti-12%-SBA-15 still
exhibits a limited recyclability, it is a highly active solid catalyst. This
opens avenues for the use of such solid Lewis acids for the
preparation of amide-containing compounds of pharmaceutical and
biological interests.
Using Ti-12%-SBA-15-TMDS as a solid catalyst, we also tested the
nature of the amine on the activity. The unsubstituted aniline was
converted quantitatively (Fig. 7, A), but more electron rich 4-
methoxyaniline gave only 29% yield (Fig. 7, B). Since the mass
recovery with this sample was very low (about 55%), one can
assume that the formation of Lewis adducts between the substrate
and the catalyst reduces the catalytic activity. As such, electron-
poor para-nitro- and para-fluoro-anilines give higher yields,
obtaining 83% and 59%, respectively, of the amidation products
(Fig. 7, C and D) with good mass recovery. Additionally, it was
shown that the amidation of morpholine was also possible,
obtaining 70% yield of the corresponding amide.
O
O
C
O
B
A
9
9
9
NH
H
NH
NH
NO2
OMe
29%*
99%
TON=80
83%
TON=66
O
D
E
9
O
9
NH
N
O
Acknowledgements
F
The authors would like to thank the Fonds de recherche du Québec
– Nature et technologies (FRQNT) and the Natural Sciences and
Engineering Research Council of Canada (NSERC) for financial
support. Professor Ryong Ryoo and Munhee Lee (KAIST and IBS,
Republic of Korea) are acknowledged for the high resolution TEM
analyses. M.Z. would like to thank Dr. Luis C. Misal Castro and
Charles Thibault for valuable scientific advices.
70%
TON=56
59%
TON=47
Figure 7. Reaction products with corresponding yields and TON
(according to the amount of metal sites) for substituted anilines (A-
D) and morpholine (E).
References
All the products of amidation reaction are new compounds, which
were fully characterized (ESI). Unfortunately, despite the promising
catalytic results, the material Ti-12%-SBA-15-TMDS exhibited
significant loss in activity upon recycling. It was observed that the
yield of product A decreased from 99% to 56 and 16% after the
second and third cycles, respectively. It is likely that Ti is either
leaching or is deactivated upon catalysis. Further optimization of
the catalysts to increase the reactivity and the reusability is
currently ongoing.
1
2
3
T. Mukaiyama, Angew. Chem., Int. Ed., 1977, 16, 817-826.
E. J. Corey, Angew. Chem., Int. Ed., 2002, 41, 1650-1667.
M. Rueping and B. J. Nachtsheim, Beilstein J. Org. Chem.,
2010, 6, 6.
4
5
A. Corma and H. García, Chem. Rev., 2003, 103, 4307-4365.
Y. Román-Leshkov and M. E. Davis, ACS Catal., 2011, 1,
1566-1580.
10 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
Page 11 of 14
Dalton Transactions
Journal Name
6
ARTICLE
Selected articles: S. P. Sheu, H. G. Karge and R. Schlogl, J.
Catal., 1997, 168, 278-291; K. Wang, X. Wang and G. Li,
Microporous Mesoporous Mater., 2006, 94, 325-329; A.
Aucejo, M. C. Burguet, A. A. Corma and V. Fornes, Appl.
Catal., 1986, 22, 187-200; A. Jentys and J. A. Lercher,
Studies in Surface Science and Catalysis, Elsevier Science B.
V.: Amsterdam, 2001, Vol. 137; M. R. Basila, T. R. Kantner
and K. H. Rhee, J. Phys. Chem., 1964, 68, 3197-3207; Z. S.
Seddigi, React. Kinet. Catal. Lett., 2001, 73, 63-70; C. Costa,
I. P. Dzikh, J. M. Lopes, F. Lemos and F. R. Ribeiro, J. Mol.
Catal. A: Chem., 2000, 154, 193-201; L. Shirazi, E. Jamshidi
and M. R. Ghasemi, Cryst. Res. Technol., 2008, 43, 1300-
1306; J. Datka and E. J. Tuznik, Catal., 1986, 102, 43-51; P. L.
Benito, A. G. Gayubo, A. T. Aguayo, M. Olazar and J. Bilbao,
J. Chem. Technol. Biotechnol., 1996, 66, 183-191; C.
Covarrubias, R. Quijada and R. Rojas, Microporous
Mesoporous Mater., 2009, 117, 118-125; J. W. Ward, J.
Catal., 1970, 18, 348-350; A. Rahman, G. Lemay, A. Adnot
and S. Kaliaguine, J. Catal., 1988, 112, 453-463.
Y. S. Yan, Microporous Mesoporous Mater., 2003, 58, 105-
114; S. Hausdorf, J. Wagler, R. Mossig anVdiewF.ArtOic.le ORn.linLe.
DOI: 10.1039/C7DT00035A
Mertens, J. Phys.Chem. A, 2008, 112, 7567-7576; L. Alaerts,
E. Seguin, H. Poelman, F. Thibault-Starzyk, P. A. Jacobs and
D. E. De Vos, Chem. Eur. J., 2006, 12, 7353-7363; F. X.
Llabrés i Xamena, A. Corma and H. Garcia, J. Phys. Chem. C,
2007, 111, 80-85; J. Catal., 2007, 250, 294-298.
20 A. Corma, H. García and F. X. Llabrés i Xamena, Chem. Rev.,
2010, 110, 4606-4655.
21 Q. Huo, D. I. Margolese, U. Ciesla, D. G. Demuth, P. Y. Feng,
T. E. Gier, P. Sieger, A. Firouzi, B. F. Chmelka, F. Schuth and
G. D. Stucky, Chem. Mater., 1994, 6, 1176-1191.
22 G. J. A. A. Soler-Illia, C. Sanchez, B. Lebeau and J. Patarin,
Chem. Rev., 2002, 102, 4093-4138.
23 Y. Wan, Y. F. Shi and D. Zhao, Chem. Commun., 2007, 897-
926.
24 Y. Wan and D. Zhao, Chem. Rev., 2007, 107, 2821-2860.
7
M. Taramasso, G. Perego and B. Notari, US Patent, 4, 410,
501, 1983; L. Shamleen, KK US Patent, 4, 623, 526, 1985; US
Patent, 4, 519, 998, 1985; European Patent, B1, 0 148, 038,
1984; J. S. Reddy, R. Kumar and P. Ratnasamy, Appl. Catal,
1990, 58, L1-L4; J. S. Reddy and R. Kumar, J. Catal. 1991,
130, 440-446.
25 T. Blasco, A. Corma, M. T. Navarro and J. P. Pariente, J.
Catal., 1995, 156, 65-74.
26 M. Iglesias and F. Sánchez, Catal. Lett., 1996, 39, 153-156.
27 M. Morey, A. Davidson, H. Eckert and G.D. Stucky, Chem.
Mater., 1996, 8, 486-492.
8
9
M. A. Camblor, A. Corma, P. Esteve, A. Martinez and S.
Valencia, Chem. Commun., 1997, 795-796.
28 A. Corma, Chem. Rev., 1997, 97, 2373-2420.
W. Peng, Y. M. Liu, M. Y. He and T. Tatsumi, J. Catal., 2004,
228, 183-191; A. Corma, M. T. Navarro and F. Rey, Chem.
Commun., 1998, 1899-1900; A. Corma, P. Esteve and A.
Martinez, J. Catal., 1996, 161, 11-19.
29 Z. H. Luan, M. Hartmann, D. Zhao, W. Z. Zhou and L. Kevan,
Chem. Mater., 1999, 11, 1621-1627.
30 Z.H. Luan, J.Y. Bae and L. Kevan, Chem. Mater., 2000, 12,
3202-3207.
10 D. Farrusseng, S. Aguado and C. Pinel, Angew. Chem. Int.
Ed., 2009, 48, 7502-7513.
31 D. Zhao, Q. Huo, J. Feng, B.F. Chmelka and G. D. Stucky, J.
Am. Chem. Soc., 1998, 120, 6024-6036.
11 B. Li, K. Leng, Y. Zhang, J. J. Dynes, J. Wang, Y. Hu, D. Ma, Z.
Shi, L. Zhu, D. Zhang, Y. Sun, M. Chrzanowski and S. Ma, J.
Am. Chem. Soc., 2015, 137, 4243-4248; P. A. Wright, L.
Mitchell, M. Clarke, V. R. Seymour, S. E. M. Ashbrook, P.
Williamson, B. Ehrlichova, A. E. Anderson, N. Acerbi, L.
Daniels and R. Walton, Chem. Eur. J., 2014, 20, 17185-
17197.
32 D. Zhao, J. Feng, Q. Huo, N. Melosh, G.H. Fredrickson, B.F.
Chmelka and G.D. Stucky, Science, 1998, 279, 548-552.
33 P. Van der Voort, M. Benjelloun and E. F. Vansant, J. Phys.
Chem. B, 2002, 106, 9027-9032.
34 T. W. Kim, R. Ryoo, M. Kruk, K. P. Gierszal, M. Jaroniec, S.
Kamiya and O. Terasaki, J. Phys.Chem. B, 2004, 108, 11480-
11489; F. Kleitz, T. Czuryszkiewicz, L. A. Solovyov and M.
Lindén, Chem. Mater., 2006, 18, 5070-5079.
12 M. Fujita, Y. J. Kwon, S. Washizu and K. Ogura J. Am. Chem.
Soc., 1994, 116, 1151-1152.
13 K. Schlichte, T. Kratzke and S. Kaskel, Microporous
Mesoporous Mater., 2004, 73, 81-88.
35 T. W. Kim, F. Kleitz, B. Paul and R. Ryoo, J. Am. Chem. Soc.,
2005, 127, 7601-7610.
14 F. Gándara, B. Gomez-Lor, E. Gutiérrez-Puebla, M. Iglesias,
M. A. Monge, D. M. Proserpio and N. Snejko, Chem. Mater.,
2008, 20, 72-76.
36 A. Galarneau, D. Desplantier-Giscard, F. Di Renzo and F.
Fajula, Catal. Today 2001, 68, 191-200.
37 A. Galarneau, M. F. Driole, C. Petitto, B. Chiche, B. Bonelli,
M. Armandi, B. Onida, E. Garrone, F. Di Renzo and F. Fajula,
Microporous Mesoporous Mater. 2005, 83, 172-180.
15 S. Horike, M. Dinca, K. Tamaki and J. R. Long, J. Am. Chem.
Soc., 2008, 130, 5854-5855.
16 F. Gándara, B. Gómez-Lor, M. Iglesias, N. Snejko, E.
Gutiérrez-Puebla and A. Monge, Chem. Commun., 2009,
2393-2395.
38 K. Cassiers, T. Linssen, M. Mathieu, M. Benjelloun, K.
Schrijnemakers, P. Van der Voort, P. Cool and E. F. Vansant,
Chem. Mater., 2002, 14, 2317-2324.
17 L. Mitchell, B. Gonzalez-Santiago, J. P. S. Mowat, M. E.
Gunn, P. Williamson, N. Acerbi, M. L. Clarke and P. A.
Wright Catal. Sci. Technol., 2013, 3, 606-617.
39 D. M. Do, S. Jaenicke and G.-K. Chuah, Catal. Sci. Tech.,
2012, 2, 1417-1424.
40 U. Diaz, M. Boronat and A. Corma Proc. R. Soc. London, Ser.
A, 2012, 468, 1927-1954.
18 A. Henschel, K. Gedrich, R. Kraehnert and S. Kaskel, Chem.
Commun., 2008, 4192-4194.
41 A. Vinu, P. Srinivasu, M. Miyahara and K. Ariga, J. Phys.
Chem. B, 2006, 110, 801-806; Y. Chen, Y. Huang, J. Xiu, X.
Han and X. Bao, Appl. Catal., A, 2004, 273, 185-191; A.
Testino, I. R. Bellobono, V. Buscaglia, C. Canevali, M.
19 Selected articles: J. Gascon, A. Corma, F. Kapteijn and F. X.
LIabrés i Xamena, ACS Catal. 2014, 4, 361-378; L. M. Huang,
H. T. Wang, J. X. Chen, Z. B. Wang, J. Y. Sun, D. Y. Zhao and
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 11
Please do not adjust margins

Please do not adjust margins
Dalton Transactions
Page 12 of 14
ARTICLE
Journal Name
D’Arienzo, S. Polizzi, R. Scotti and F. Morazzoni, J. Am.
Chem. Soc., 2007, 129, 3564-3575.
63 M. V. Landau, L. Titleman, L. Vradman and P. Wilson, Chem.
View Article Online
Commun., 2003, 594-595.
DOI: 10.1039/C7DT00035A
42 Z. Luan and J. A. Fournier Microporous Mesoporous Mater.,
2005, 79, 235-240.
64 M. V. Landau, L. Vradman, X. Wang and L. Titleman,
Microporous Mesoporous Mater., 2005, 78, 117-129.
43 I. Jiménez-Morales, J. Santamaría-González, P Maireles-
Torres and A. Jiménez-López Appl. Catal. B, 2011, 105, 199-
205; M. Gómez-Cazalillaa, J. M. Mérida-Roblesa, A.
Gurbanib, E. Rodríguez-Castellóna and A. Jiménez-López, J.
Solid State Chem., 2007, 180, 1130-1140.
65 V. Degirmenci, O. F. Erdum, A. Yilmaz, D. Michel and D.
Uner, Catal. Lett., 2007, 115, 79-85.
66 L. Vradman, M. V. Landau, M. Herskowitz, V. Ezersky, M.
Talianker, S. Nikitenko, Y. Koltypin and A. Gedanken, J.
Catal., 2003, 213, 163-175.
44 A. Kuschel and S. Polarz, J. Am. Chem. Soc., 2010, 132,
67 C. K. Krishnan, T. Hayashi and M. Ogura Adv. Mater., 2008,
20, 2131-2136.
6558-6565.
45 J. Jarupatrakorn and T. D. Tilley, J. Am. Chem. Soc., 2002,
124, 8380-8388; R. L. Brutchey, D. A. Ruddy, L. K. Andersen
and T. D. Tilley, Langmuir , 2005, 21, 9576-9583.
68 J. Sauer, F. Marlow, B. Spliethoff and F. Schüth, Chem.
Mater., 2002, 14, 217-224.
69 V. Bosbeek, D. Freude, T. Frohlich, H. Pfeifer and H.
Schmiedel, J. Colloid Interface Sci., 1982, 85, 502-507; D.
Freude, T. Frohlich, H. Pfeifer and G. Scheler, Zeolites, 1983,
3, 171-177.
46 F. Bérubé, F. Kleitz and S. Kaliaguine J. Phys. Chem. C, 2008,
112, 14403-14411.
47 T.-W. Kim, M.-J. Kim, F. Kleitz, M. M. Nair, R. Guillet-Nicolas,
K.-E. Jeong, H.-J. Chae, C.-U. Kim and S.-Y. Jeong,
ChemCatChem, 2012, 4, 687-697; F. Bérubé, B. Nohair, F.
Kleitz and S. Kaliaguine Chem. Mater., 2010, 22, 1988-2000.
70 M. Yurdakoç, M. Akçay, Y. Tonbul and K. Yurdakoç, Turk. J.
Chem., 1999, 23, 319-328; K. Tanebe, M. Misono, Y. Ono
and H. Hattori, New Solid Acids and Bases, Their Catalytic
Properties, Studies in Surface Science and Catalysis, Elsevier,
Amsterdam, 1989, 51; K. Wang, X. Wang and G. Li,
Microporous Mesoporous Mater., 2006, 94, 325-329.
48 N. K. Shintaku, K. Nakajima, M. Kitano, N. Ichikuni and M.
Hara ACS Catal., 2014, 4, 1198-1204.
49 D. J. C. Constable, P. J. Dunn, J. D. Hayler, G. R. Humphrey, J.
J. L. Leazer, R. J. Linderman, K. Lorenz, J. Manley, B. A.
Pearlman, A. Wells, A. Zaks and T. Y. Zhang, Green Chem.,
2007, 9, 411-420.
71 A. Aucejo, M. C. Burguet, A. A. Corma and V. Fornes, Appl.
Catal., 1986, 22, 187-200.
72 Y. Sun, L. Zhu, H. Lu, R. Wang, S. Lin, D. Jiang and F.-S. Xiao,
50 S. D. Roughley and A. M. Jordan, J. Med. Chem., 2011, 54,
Appl. Catal. A, 2002, 237, 21-31.
3451-3479.
73 Y. Rao and D. M. Antonelli, J. Mater. Chem., 2009, 19, 1937-
51 J. S. Carey, D. Laffan, C. Thomson and M. T. Williams, Org.
Biomol. Chem., 2006, 4, 2337-2347.
1944.
74 T. Alemdaroglu, Commun. Fac. Sci. Univ. Ank. Series B,
2001, 47, 27-35.
52 E. Valeur and M. Bradley, Chem. Soc. Rev., 2009, 38, 606-
631.
75 K. S. Ishihara, K. H. Ohara and K. Yamamoto, J. Org. Chem.,
1996, 61, 4196-4197; T. Maki, K. Ishihara and H. Yamamoto,
Org. Lett., 2006, 8, 1431-1434; R. Yamashita, A. Sakakura
and K. Ishihara, Org. Lett., 2013, 15, 3654-3657; N.
Gernigon, R. M. Al-Zoubi and D. G. Hall, J. Org. Chem., 2012,
77, 8386-8400; R. M. Al-Zoubi, O. Marion and D. G. Hall,
Angew. Chem. Int. Ed., 2008, 47, 2876-2879; R. M. Al-Zoubi,
O. Marion and D. G. Hall, Angew. Chem., Int. Ed., 2008, 120,
2918-2921; K. Arnold, A. S. Batsanov, Davies and B. A.
Whiting, Green Chem., 2008, 10, 124-134; E. K. W. Tam and
L. Y. Liu, A. Chen, Eur. J. Org. Chem., 2015, 1100-1107; R. M.
Lanigan, P. Starkov and T. D. Sheppard, J. Org. Chem., 2013,
78, 4512-4523; D. C. Lenstra, F. P. J. T. Rutjes and J.
Mecinović, Chem. Commun., 2014, 50, 5763-5766.
53 M. A. Ali, S. M. A. H. Siddiki, W. Onodera, K. Kon and K.
Shimizu, ChemCatChem, 2015, 7, 3555-3561.
54 A. Sakthivel, K. Komura, S.-J. Huang, P.-H. Wu, S.-Bi. Liu, Y.
Sasaki and Y. Sugi, Ind. Eng. Chem. Res., 2010, 49, 65-71.
55 M. Hosseini-Sarvari and H.Sharghi, J. Org. Chem., 2006, 71,
6652-6654.
56 J. W. Comerford, J. H. Clark, D. J. Macquarrie and S. W.
Breeden, Chem. Commun., 2009, 2562-2564; N. Narender,
P. Srinivasu, S. J. Kulkarni and K. V. Raghavan, Green Chem.,
2000, 104-105; B.M. Choudary, V. Bhaskar, M. Lakshmi
Kantam, K. Koteswara Rao and K.V. Raghavan, Catal. Lett.,
2001, 207-211; P. S. Chaudhari, S.D. Salim, R. V. Sawant and
K. G. Akamanchi, Green Chem., 2010, 12, 1707-1710.
76 T. Maki, K. Ishihara and H. Yamamoto, Org. Lett., 2005, 7,
5043-5046.
57 Y. Liang and A. Reiner, J. Mater. Chem., 2007, 17, 2506-
77 Selected articles: H. Lundberg, F. Tinnis and H. Adolfsson,
Chem.-Eur. J., 2012, 18, 3822-3826; C. L. Allen, A. R. Chatwal
and J. M. J. Williams, Chem. Commun., 2012, 48, 666-668; F.
Tinnis, H. Lundberg and H. Adolfsson, Adv. Synth. Catal.,
2012, 354, 2531-2536; Synlett, 2012, 2201-2204; A. C.
Shekhar, A. R. Kumar, G. Sathaiah, V. L. Paul, M. Sridhar and
P. S. Rao, Tetrahedron Lett., 2009, 50, 7099-7101; Y.
Terada, N. Ieda, K. Komura and Y. Sugi, Synthesis, 2008,
2318-2320; K. Steliou and M. A. Poupart, J. Am. Chem. Soc.,
1983, 105, 7130-7138.
2516.
58 C. Walling, J. Am. Chem. Soc., 1950, 72, 1164-1168.
59 O. Johnson, J. Phys. Chem., 1955, 59, 827-831.
60 H. A. Benesi, J. Phys. Chem., 1957, 61, 970-973.
61 F. Schuth, A. Wingen and J. Sauer, Microporous Mesoporous
Mater., 2001, 44–45, 465-476.
62 W. Hua, Y. Yue and Z. Gao, J. Mol. Catal. A: Chem., 2001,
170, 195-202.
78 H.-S. H. Sharghi, J. Org. Chem., 2006, 71, 6652-6654.
12 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
Page 13 of 14
Dalton Transactions
Journal Name
ARTICLE
79 V. K. Das, R. R. Devi, P. K. Raul, and A. Thakur, Green Chem.,
2012, 14, 847-854.
View Article Online
DOI: 10.1039/C7DT00035A
80 B. M. Choudary, V. Bhaskar, M. L. Kantam, K. K. Rao and K.
V. Raghavan, Catal. Lett., 2001, 74, 207-211.
81 E. Calcio Gaudino, D. Carnaroglio, M. A. G. Nunes, L.
Schmidt, E. M. M. Flores, C. Deiana, Y. Sakhno, G. Martra
and G. Cravotto, Catal. Sci. Tech., 2014, 4, 1395-1399.
82 S. Nagarajan, P. Ran, P. Shanmugavelan, M. Sathishkumar,
A. Ponnuswamy, K. S. Nahm and G. G. Kumar, New J. Chem.,
2012, 36, 1312-1319.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 13
Please do not adjust margins

Dalton Transactions
Page 14 of 14
View Article Online
DOI: 10.1039/C7DT00035A
Water-tolerant metal supported Lewis acids were synthesized for the catalytic amidation of electron-poor and bulky
amines.