Organic-inorganic hybrid supermicroporous iron(III) phosphonate nanoparticles as an efficient catalyst for the synthesis of biofuels

Article abstract of DOI:10.1002/chem.201300128

Here we report a novel family of crystalline, supermicroporous iron(III) phosphonate nanomaterials (HFeP-1-3, HFeP-1-2, and HFeP-1-4) with different Fe^III-to-organophosphonate ligand mole ratios. The materials were synthesized by using a hydrothermal reaction between benzene-1,3,5-triphosphonic acid and iron(III) chloride under acidic conditions (pH≈4.0). Powder X-ray diffraction, N₂ sorption, transmission and scanning electron microscopy (TEM and SEM) image analysis, thermogravimetric and differential thermal analysis (TGA-DTA), and FTIR spectroscopic tools were used to characterize the materials. The triclinic crystal phase [P1(2) space group] of the hybrid iron phosphonate was established by a Rietveld refinement of the PXRD analysis of HFeP-1-3 by using the MAUD program. The unit cell parameters are a=8.749(1), b=8.578(1), c=17.725(3) ?; α=104.47(3), β=97.64(1), γ=113.56(3)°; and V=1013.41 ?³. With these crystal parameters, we proposed an 24-membered-ring open framework structure for HFeP-1. Compound HFeP-1-3, with an starting Fe/ligand molar ratio of 3.0, shows the highest Brunauer-Emmett-Telller (BET) surface area of 556 m²g ^-1 and uniform supermicropores of approximately 1.1 nm. The acidic surface of the porous iron(III) phosphonate nanoparticles was used in a highly efficient and recyclable catalytic transesterification reaction for the synthesis of biofuels under mild reaction conditions. Iron brews biofuels: Highly crystalline, supermicroporous iron(III) phosphonate nanoparticles have been synthesized through a hydrothermal reaction between benzene-1,3,5- triphosphonic acid and FeCl₃. The resulting material was used as an efficient and recyclable catalyst for the synthesis of biofuels under mild reaction conditions (see scheme). Copyright

Full text of DOI:10.1002/chem.201300128

FULL PAPER
DOI: 10.1002/chem.201300128
Organic–Inorganic Hybrid SuperACTHNUGTRENNUGmicroporous IronACHTUNGTERN(NUGN III) Phosphonate
Nanoparticles as an Efficient Catalyst for the Synthesis of Biofuels
Malay Pramanik and Asim Bhaumik*[a]
Abstract: Here we report
family of crystalline, supermicroporous
iron(III) phosphonate nanomaterials
(HFeP-1-3, HFeP-1-2, and HFeP-1-4)
with different FeIII-to-organophospho-
nate ligand mole ratios. The materials
were synthesized by using a hydrother-
mal reaction between benzene-1,3,5-tri-
a
novel
FTIR spectroscopic tools were used to
characterize the materials. The triclinic
crystal phase [P1(2) space group] of
the hybrid iron phosphonate was estab-
lished by a Rietveld refinement of the
PXRD analysis of HFeP-1-3 by using
the MAUD program. The unit cell pa-
rameters are a=8.749(1), b=8.578(1),
1013.41 ꢀ3. With these crystal parame-
ters, we proposed an 24-membered-
ring open framework structure for
HFeP-1. Compound HFeP-1-3, with an
starting Fe/ligand molar ratio of 3.0,
shows the highest Brunauer–Emmett–
Telller (BET) surface area of 556 m2gÀ1
and uniform supermicropores of ap-
proximately 1.1 nm. The acidic surface
¯
U
phosphonic acid and iron
N
c=17.725(3) ꢀ;
a=104.47(3),
b=
under acidic conditions (pHꢀ4.0).
Powder X-ray diffraction, N2 sorption,
transmission and scanning electron mi-
croscopy (TEM and SEM) image anal-
ysis, thermogravimetric and differential
thermal analysis (TGA-DTA), and
97.64(1), g=113.56(3)8; and V=
of the porous ironACTHNGUTRENNU(G III) phosphonate
nanoparticles was used in a highly effi-
cient and recyclable catalytic trans-
AHCTUNGTRENNGeUN sterification reaction for the synthesis
of biofuels under mild reaction condi-
tions.
Keywords: biofuel synthesis · iron ·
microporous materials · organic–in-
organic hybrids · transesterification
Introduction
ty and crystallinity is very demanding. A strong coordination
interaction is required to sustain pores, but at the same time
stronger interactions could make the periodicity of the pore
apertures more challenging.[7]
The design of novel porous nanomaterials with extended
network topologies is one of the most demanding and chal-
lenging areas of research due to the widespread potential
applications of these materials in molecular reorganization,
sensing, selective catalysis, gas adsorption/storage, and so
on.[1] Of the three most widely studied categories of porous
nanomaterials, purely inorganic frameworks (such as zeo-
lites, metallophosphates, and oxides[2]), porous organic poly-
mers,[3] and organic–inorganic hybrid frameworks,[4] the last
has attracted increasing attention in recent times. Although
there are many reports on the synthesis of extra-large pore
or supermicroporous materials with completely inorganic
framework compositions,[5] the lack of flexibility of the inor-
ganic frameworks and their inertness towards further func-
tionalization has motivated researchers to explore porous
organic–inorganic hybrid supermicroporous frameworks.
When tuning the organic spacer groups in these porous ar-
chitectures, one can easily tune the pore size and surface
chemical properties associated with them.[6] However, the
synthesis of targeted hybrid materials with nanoscale porosi-
Because carboxylate and pyridine derivatives induce mod-
erately strong metal–ligand coordination in secondary build-
ing units (SBUs), they are generally used as the organic
linkers when both porosity and crystallinity are targeted.[8]
Thus, most of the metal–organic frameworks (MOFs) re-
ported to date are composed of either carboxylate- or pyri-
dine-based organic scaffolds.[9] In comparison, phosphonate-
based organic linkers, such as linear monophosphonic acid
or diphosphonic acid, offer stronger bonding and a tendency
to pack efficiently between the inorganic species.[10] Al-
though there are reports of metal–organophosphonates
based on monophosphonic acid or diphosphonic acid as the
organic spacer groups,[11] their mechanical and thermal sta-
bility is restricted due to limited cross-linking. Thus, to en-
hance the cross-linking in the porous framework through
multidentate phosphonic acid sites of the ligand as an organ-
ic scaffold, a triphosphonic acid (benzene-1,3,5-triphosphon-
ic acid) can be used as an organic linker between the inor-
ganic metal ions. Over the last few years we have been
working to design supermicroporous hybrid materials[12] that
can expand the scope of catalysis beyond microporous zeo-
lite[13] and can bridge between microporous (<1.0 nm) and
mesoporous (>2.0 nm) materials.[14] Herein we report a new
[a] M. Pramanik, Prof. Dr. A. Bhaumik
Department of Materials Science
Indian Association for the Cultivation of Science
Jadavpur, Kolkata, 700 032 (India)
E-mail: msab@iacs.res.in
supermicroporous
(HFeP-1-3), which has a high BET surface area (556 m2 gÀ1)
and a highly crystalline framework. To the best of our
material,
iron
G
phosphonate
AHCTUNGTRENNUNG
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201300128.
Chem. Eur. J. 2013, 00, 0 – 0
ꢁ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
1
&
ÞÞ
These are not the final page numbers!

knowledge, this is the first report of porous organic–inorgan-
ic hybrid iron
(III) phosphonate nanoparticles[15] of ultra-
small size (3.0–5.0 nm) together with the presence of a
mesophase (under a non-templating synthesis route) and
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
high BET surface area. The beauty of this family of porous
materials lies behind the control of porosity and material
properties, which keep the crystal structure intact just by
tuning the metal-to-organophosphorus precursor mole
ratio.[16] Thus, one can chemically control the pore size and
other surface properties of this new family of nanoporous
iron phosphonate nanoarchitectures.
In this context, it is pertinent to mention that the demand
for biofuels is increasing day by day because they are a re-
newable source of energy that does not emit any hazardous
components (sulfur, aromatic compounds).[17] The limited
supply of fossil fuel, emission of greenhouse gases, and re-
peated oil price hikes have motivated researchers to design
suitable catalysts for the synthesis of biofuels.[18] Generally,
biofuels are produced by a catalytic transesterification reac-
tion of animal fats or vegetable oils by short-chain aliphatic
alcohols.[19] Thus, a wide range of research activities have
been focused on designing suitable acid catalysts for the
transesterification reaction.[20] Furthermore, this reaction
can also proceed in basic catalytic medium in a facile way.[21]
Herein, we report novel organic–inorganic hybrid iron phos-
phonates synthesized by varying the FeIII-to-benzene-1,3,5-
triphosphonic acid molar ratio under mild hydrothermal
conditions; the surface acidity of the materials was used in
catalytic transesterification reactions under solvent-free con-
ditions. The hybrid iron phosphonate catalyst can be easily
separated by using a simple filtration technique and can be
reused five times without significant loss of catalytic activity.
Figure 1. Small-angle powder XRD pattern of HFeP-1-3.
Figure 2. Wide-angle powder XRD pattern of HFeP-1-3 (&), HFeP-1-4
(c), HFeP-1-2 (g).
the standard JCPDS literature profiles. Thus, to establish
the crystal structure of the porous crystalline material we
carried out a Rietveld refinement[23] by employing the
MAUD program.[24] After final refinement, the X-ray dif-
fraction pattern of these materials could be assigned to a tri-
Results and Discussion
Here we have synthesized a series of three ironACHTNUTRGNE(UNG III) phos-
phonate materials (HFeP-1) in which the benzene-1,3,5-tri-
phosphonic acid-to-FeIII molar ratios were 1:3, 1:2, and 1:4,
designated as HFeP-1-3, HFeP-1-2, and HFeP-1-4, respec-
tively. Of these three hybrid iron phosphonate materials,
HFeP-1-3 was extensively studied because it showed the
highest BET surface area.
¯
clinic crystal phase with the P1(2) space group. The corre-
sponding unit cell parameters are as follows a=8.749(1), b=
8.578(1), c=17.725(3) ꢀ; a=104.47(3)8, b=97.64(1), g=
113.56(3)8; V=1013.41 ꢀ3 (Table 1). The powder XRD pat-
tern of the material with the final Rietveld refinement and
the difference plot are given in Figure 3. The very small
goodness of fit (GOF) value (2.315) is in quite good agree-
ment with the fitting between the theoretical curve and the
experimental one. The unit cell parameters and the reflec-
tions from the different planes (hkl) with the corresponding
d spacing are listed in Table 2.
Framework and nanostructure: The small-angle powder dif-
fraction pattern of HFeP-1-3 is shown in Figure 1. A single
very broad peak centered at approximately 2q=2.588 could
be attributed to the uniform assembly of mesoscopic void
spaces created by the aggregation of very tiny nanoparti-
cles.[22] The inter-particle distance corresponding to this
small angle peak is 3.42 nm, which suggests that HFeP-1-3 is
composed of very tiny self-assembled nanoparticles that are
responsible for this mesophase. The wide-angle X-ray dif-
fraction patterns of the materials (HFeP-1-3, HFeP-1-2, and
HFeP-1-4) are shown in Figure 2. The crystallinity of this
hybrid material is sufficiently high and the wide-angle
PXRD patterns of the materials do not match with any of
Bonding and framework structure: The FTIR spectrum of
HFeP-1-3 between 4000 and 400 cmÀ1 is shown in Figure 4.
The band centered at 544 cmÀ1 could be assigned to the
À
characteristic stretching vibration of the Fe O group. The
set of bands at 966 and 1062 cmÀ1 was assigned to the
stretching vibration of the tetrahedral CPO3 group.[25] The
presence of a benzene ring in the hybrid framework could
&
2
&
www.chemeurj.org
ꢁ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 0000, 00, 0 – 0
ÝÝ
These are not the final page numbers!

Organic–Inorganic Hybrid Supermicroporous Nanoparticles
Table 1. Crystal parameters of HFeP-1-3.
FULL PAPER
chemical formula
C6P3O11.50Fe2.77
504.38
Mr [gmolÀ1
]
symmetry
space group
a [ꢀ]
b [ꢀ]
c [ꢀ]
triclinic
P1(2)
¯
8.74(1)
8.57(1)
17.72(3)
104.47(3)
97.64(1)8
113.56(3)8
1013
a [8]
b [8]
g [8]
V [ꢀ3]
Z
2
1exptl [gcmÀ3
]
]
1.6231
1.6538
1.5406
10ꢁ2qꢁ50
0.02 (w)
25
1calcd [gcmÀ3
l [ꢀ]
range of data collection
angle step [8]
time per step [s]
contributing reflns
reliability factors
Figure 4. FTIR spectrum of HFeP-1-3.
529
be inferred from characteristic vibration bands at 1414 and
1593 cmÀ1. The peak at 1632 cmÀ1 could be due to the bend-
ing vibration of water molecules. The broad band centered
R
wP =0.031
Rp =0.023
2.315
GOF
at 3394 cmÀ1 was assigned to the defected P OH group in
À
the porous architecture and the free water molecules attach-
ed to the surface of HFeP-1-3 through hydrogen bonding.[26]
Thus, this FTIR spectroscopic result suggested the presence
of benzene-1,3,5-triphosphonic acid in the porous frame-
work of HFeP-1.
Electron microscopy analysis: The representative TEM
images of the HFeP-1-3 sample are shown in Figure 5a. The
black spots (indicated by dotted white circles) throughout
the specimens in Figure 5a are representative nanoparticles
of HFeP-1-3 with dimensions of approximately 3 to 5 nm. In
the same figure, the white spots (indicated by solid white cir-
cles) indicate pores with dimensions of approximately
1.08 nm. Figure 5b shows the high-resolution TEM image of
HFeP-1-3. Lattice fringes in the HR-TEM image suggest the
high crystallinity of the material. The corresponding d spac-
!
Figure 3. Fitting of the wide-angle XRD pattern of HFeP-1-3 ( ) with
the theoretical pattern (&). The difference is indicated by g.
Table 2. Indexing of the triclinic crystal structure of HFeP-1-3.
h
k
l
2q [8]
d
0
1
1
0
1
1
1
3
2
1
4
5
5
2
5
4
1
3
4
0
6
5
5
11.732
12.803
13.601
14.903
16.401
16.851
20.358
23.801
26.830
28.631
31.423
33.161
35.602
37.161
39.684
40.811
43.110
44.180
45.870
48.602
7.536
6.908
6.504
5.939
5.4
5.256
4.358
3.735
3.32
3.115
2.844
2.699
2.519
2.417
2.269
2.209
2.096
2.048
1.976
1.871
À1
À1
1
0
1
0
À1
À1
À2
1
0
1
1
1
À1
0
À1
À3
À2
0
1
À1
2
3
À3
À2
À1
1
1
2
3
À3
3
1
À4
Figure 5. a) TEM image, and b) HR-TEM image and corresponding FFT
pattern of HFeP-1-3.
À1
3
Chem. Eur. J. 2013, 00, 0 – 0
ꢁ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
&
3
&
ÞÞ
These are not the final page numbers!

A. Bhaumik and M. Pramanik
in Figure 7. The 24-membered-ring open porous architecture
shown in Figure 7 has a pore aperture of about 1.0 nm and
the molecular formula of the model structure is
Fe3P3O11C6H7. The atomic positions and the corresponding
bond lengths and bond angles for the proposed structure are
listed in Tables S1 and S2 in the Supporting Information. El-
emental analysis of the materials revealed that the HFeP-1-
3, HFeP-1-2, and HFeP-1-4 contain 30.71, 22.76, and
34.69 wt% of iron, respectively (estimated by using AAS
analysis). The CHN analysis of HFeP-1-3, HFeP-1-2, and
HFeP-1-4 shows that the materials contain 14.31, 14.12, and
13.40 wt% carbon (C), 2.430, 2.301, and 1.876 wt% hydro-
gen (H), and 0 wt% nitrogen (N) in the porous frameworks.
The TGA analysis curve is also in good agreement with the
amount of organic carbon (C) present in the porous frame-
works. The amount of phosphorus (P) and oxygen (O) de-
termined from the EDS analysis is shown in Table 3 (see the
Supporting Information, Figure S3). From the elemental
data analysis the molecular formula of the materials can be
assigned as C6P3O11.50Fe2.77 for HFeP-1-3, C6P3O14.32Fe2.08 for
HFeP-1-2, and C6P3O11.64Fe3.34 for HFeP-1-4. In the model
structure (Figure 7) the molar ratios are C/Fe=0.43, O/Fe=
1.05, and P/Fe=0.55. In HFeP-1-3 the corresponding molar
ratios are C/Fe=0.46, O/Fe=1.15, and P/Fe=0.59; for
HFeP-1-2 the ratios are C/Fe=0.62, O/Fe=1.95, and P/Fe=
0.80; and for HFeP-1-4 the ratios are C/Fe=0.39, O/Fe=
1.01, and P/Fe=0.50. The theoretical density of the model
Figure 6. SEM image of HFeP-1-3.
ing between the crystal planes is 3.30 and 2.13 ꢀ (as seen in
Figure 5b). These values are in quite good agreement with
the d spacing of the (005) and (130) crystal planes of a tri-
clinic crystal phase with unit cell parameters of a=8.749,
b=8.578, c=17.725 ꢀ; a=104.47, b=97.64, g=113.568. The
FE-SEM image of a representative sample of HFeP-1-3 is
shown in Figure 6. Finely monodispersed spherical nanopar-
ticles with dimensions of approximately 3.0 to 4.0 nm are
seen throughout the specimen. The HFeP-1-2 and HFeP-1-4
samples also showed very tiny spherical nanosphere-like
morphological features (see the Supporting Information,
Figure S1a–b). The mesoporosity in the material is thus at-
tributed to the aggregation of finely dispersed nanoparticles.
Thermal analysis: The stability of the porous ironACTHNUTRGENUG(N III) phos-
phonate architecture (HFeP-1-3) has been determined from
thermogravimetric and differen-
tial thermal analysis (TGA-
DTA) under a continuous flow
of nitrogen (N2) with a heating
rate of 108CminÀ1. The TGA-
DTA profile of HFeP-1-3 is
shown in the Supporting Infor-
mation (Figure S2). The TGA
plot shows three distinct weight
losses. The first endothermic
weight loss (15.2%) up to
420 K corresponds to the loss of
water molecules present in the
porous framework. The second
and third exothermic weight
losses (total 17.6%) in the
range of 420 to 1130 K corre-
À
spond to the breaking of C C
À
and C P bonds and the burning
of organics present in the
porous framework.
Molecular formulae of the iron-
ACHTUNGTRENNUNG(III) phosphonate organic–inor-
ganic hybrids: To understand
the connectivity of atoms in the
porous framework, we have
proposed a model with the crys-
tal parameters (abstracted from
the final Rietveld refinement) Figure 7. Ball-and-stick model of HFeP-1-3 showing the pore aperture.
&
4
&
www.chemeurj.org
ꢁ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 0000, 00, 0 – 0
ÝÝ
These are not the final page numbers!

Organic–Inorganic Hybrid Supermicroporous Nanoparticles
Table 3. EDS elemental composition of the materials.
FULL PAPER
Mass [%]
Atomic [%]
HFeP-1-3 HFeP-1-2 HFeP-1-4 HFeP-1-3 HFeP-1-2 HFeP-1-4
C
O
P
15.31
36.53
18.45
15.63
44.90
18.21
21.26
13.90
34.63
17.28
34.19
28.32
44.45
14.16
13.07
26.31
51.34
13.15
9.12
27.43
43.36
13.71
15.50
Fe 29.71
structure was calculated to be 1.688 gcmÀ3 and the calculat-
ed densities for HFeP-1-3, HFeP-1-2, and HFeP-1-4 are
1.653, 1.672, and 1.760 gcmÀ3, respectively. From the above
results it is clear that the model structure proposed in
Figure 7 is quite valid for HFeP-1-3 and HFeP-1-4 but for
HFeP-1-2 there is some discrepancy between the model
structure and the chemical formula. This discrepancy is
probably due to the lower iron content, which produces
defect phosphonate sites in the porous architecture of
HFeP-1-2.
Figure 8. N2 adsorption and desorption isotherms for HFeP-1-3 and
*
HFeP-1-4. The adsorption of HFeP-1-3 is indicated by
and that of
~
*
HFeP-1-4 by ; the corresponding desorption points are marked by
~
and , respectively.
Surface area and porosity: The architectural porosity in the
family of hybrid iron phosphonate nanomaterials is demon-
strated by the respective N2 adsorption measurement at
77 K. The corresponding Brunauer–Emmett–Telller (BET)
surface area (for microporosity and mesoporosity), pore di-
ameters, and pore volumes for the materials are shown in
Table 4. The N2 adsorption and desorption isotherms for
Table 4. Porosity and BET surface areas of different hybrid iron
phosphonates.
ACHTUNGTNER(NUNG III)
&
Figure 9. NLDFT pore size distribution for HFeP-1-3 ( ) and for HFeP-
*
1-4 ( ).
Sample (L/Fe)
BET surface
area [m2 gÀ1
total micro external
Pore volume Peak pore
]
A
]
widths [nm]
source are coordinated to the metal ion to give
a
24-member-ring open channel with a 1.1 nm pore aperture
(Figure 7). Here, the type I isotherm for the material sup-
ports the presence of microporous channels in the porous ar-
chitecture, whereas the mesoporosity (2.1 nm) could arise
due to the generation of interparticle voids through the ag-
gregation of almost monodisperse tiny nanoparticles. How-
ever, for HFeP-1-2, with L/M=1:2, every phosphonic acid
side chain of the precursor molecule is not coordinated in a
similar fashion, although the overall crystal structure re-
mains the same. Here some inhomogeneity arises in the
porous framework, which is reflected in the NLDFT pore
size distribution curve. Thus, HFeP-1-2 shows hierarchical
porosity with a type IV isotherm together with an H3 type
hysteresis loop (Figure S4 in the Supporting Information). If
the metal concentration in the porous framework is further
increased to 1:4, the open channel in HFeP-1-3 becomes
somehow blocked; this is reflected in the lowering of the
surface area and pore volume of HFeP-1-4.
HFeP-1-2 (1:2) 251
HFeP-1-3 (1:3) 556
HFeP-1-4 (1:4) 286
33
490
223
218
67
63
0.3448
0.2932
0.1773
1.3, 3.1, 5.4
1.1, 2.1
1.1, 2.6
HFeP-1-2 (benzene-1,3,5-triphosphonic acid-to-ironACHTUNTRGNEUNG(III)
mole ratio 1:2) shows a type IV isotherm (Figure S4 in the
Supporting Information)[27] with an H3 type desorption hys-
teresis loop.[28] The pore size distribution estimated by using
nonlocal density functional theory (NLDFT)[29] is shown in
the inset of Figure S4 and suggests interparticle mesoporosi-
ty. Conversely, the HFeP-1-3 and HFeP-1-4 samples with
ironACHTUNGTRENNUNG(III)-to-benzene-1,3,5-triphosphonic acid mole ratios of
3 and 4 show mostly type I sorption isotherms (Figure 8)
that correspond to microporous materials.[28] The corre-
sponding pore size distributions of these materials were also
determined by using an NLDFT method and are given in
Figure 9. Thus, the percentage of metal FeIII present in the
hybrid materials considerably affects the surface area of this
new family of porous metal–phosphonate framework. The
proposed model explains quite well the drastic changes in
BET surface area of the materials together with the change
in the nature of the N2 sorption isotherm. For HFeP-1-3,
with L/M=1:3, there is a high possibility that most of the
ligand phosphonic acid groups of the organophosphorous
Catalysis: The increasing demand for biofuels has in recent
times generated new interest in the transesterification reac-
tion, which is usually catalyzed by strong acid or basic sites.
The conversion of different reactant esters to their corre-
sponding methyl esters over our organic–inorganic hybrid
supermicroporous ironACHTUNRGTNE(NUG III) phosphonate material is given in
Chem. Eur. J. 2013, 00, 0 – 0
ꢁ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
&
5
&
ÞÞ
These are not the final page numbers!

A. Bhaumik and M. Pramanik
Table 5. Catalytic activity of HFeP-1-3 in the transesterification
reaction.[a]
cates the catalytic role played by HFeP-1-3 in this transes-
terification reaction. It is pertinent to mention that the
amount of HFeP-1-3 catalyst necessary for this transesterifi-
cation reaction is very low (1.0 wt% with respect to the re-
actant ester only). When the reaction was carried out in the
presence of a relatively large amount of the catalyst, the
yield did not improve (Table 5, entry 6). A low catalyst
amount is in turn good for higher turnover and throughput
of the reaction. We used HFeP-1-3 for five successive cata-
lytic cycles with ethyl cyanoacetate as the representative
ester in this transesterification reaction. After the fifth cycle,
the yield of methylcyanoacetate was 85.6%, compared with
88.9 in the first cycle (see Figure 10). This result suggests
Entry
Substrate
Conversion [%]
Selectivity [%]
1
2
3
4
5
6
ethyl cyanoacetate
ethyl acetoacetate
ethyl chloroacetate
ethyl acrylate
88.3
71.2
43.2
23.7
3.8
100
80
100
100
92
ethyl cyanoacetate[b]
ethyl acrylate[c]
24.0
96
[a] Reaction conditions: Catalyst=1 wt% with respect to the reactant
ester, reaction temperature=333 K. The conversion and selectivity were
measured by using GC analysis. [b] The reaction was carried out in the
absence of HFeP-1-3; [c] 5 wt% catalyst was used.
Table 5. Ethyl cyanoacetate showed maximum conversion in
the transesterification reaction over HFeP-1-3. For a hetero-
genous catalytic reaction over a porous framework, it is cru-
cial that the reactants and the catalytically active sites of the
catalyst can come into close proximity.[30] Here, the catalyti-
cally active FeIII sites in HFeP-1-3 are present at the internal
surfaces of the pores. Thus, for the carbonyl group of the
ester to reach the active sites, the molecules have to intro-
duce into the porous channel through the 1.1 nm pore aper-
ture. We have proposed a mechanism for this transesterifica-
tion reaction in Scheme 1. The electrophilicity of the car-
Figure 10. Recycling efficiency of hybrid iron phosphonate catalyst
HFeP-1-3.
that HFeP-1-3 is a very efficient and recyclable catalyst for
the transesterification reaction. We have also studied the
catalytic
transesterification
reactions
of
ethyl
Scheme 1. Proposed mechanism of the transesterification reaction over
HFeP-1-3.
cyanoacetate over HFeP-1-2 and HFeP-1-4 under the same
reaction conditions; the results are shown in Table 6. A rela-
tively lower product yield over both HFeP-1-2 and
HFeP-1-4 compared with HFeP-1-3 suggested that the
higher surface area of the latter played a crucial role in the
transesterification reaction.
bonyl carbon of the reactant ester group is the main driving
force of the reaction. The electron-withdrawing effect (ÀI)
of the different species is as follows CN>C(O)CH3 >Cl.[31]
From Table 5, we can see that as the ÀI effect of the sub-
stituent to the ethyl-substituted acid group decreases, the
conversion to the lower alkyl-substituted ester decreases.
Negatively charged free phosphonic acids in the porous
framework could prevent molecules enriched with p-elec-
tron clouds from entering the porous channels. Thus, the p
electrons could be responsible for the minimal conversion of
ethyl acrylate to the corresponding transesterified product
compared with the other targeted esters. Ethylene glycoldi-
methyacrylate, which is overcrowded with a p-electron
cloud, is quite unable to enter into the porous framework
and thus did not show any conversion in the transesterifica-
tion reaction over HFeP-1-3. Therefore, the catalyst can be
selectively used for the transesterification reaction for esters
that contain fewer mobile electrons.[32] When the reaction
was carried out in the absence of any catalyst, very poor
conversion was observed (Table 5, entry 5). This result indi-
Table 6. Catalytic activity of HFeP-1-2 and HFeP-1-4 in the transesterifi-
cation reaction.[a]
Substrate
Yield [%]
Selectivity [%]
HFeP-1-2
HFeP-1-4
ethyl cyanoacetate
ethyl cyanoacetate
84.7
71.3
100
100
[a] Reaction conditions: Catalyst=1 wt% with respect to the reactant
ester, reaction temperature=333 K. The conversion and selectivity were
measured by using GC analysis.
Conclusion
A new supermicroporous ironACHTNUTRGNE(UNG III) phosphonate nanomateri-
al with a triclinic crystal phase and P1(2) space group can
be designed through a hydrothermal reaction between ben-
zene-1,3,5-triphosphonic acid and ironACTHNUTRGNEUNG(III) chloride. Hybrid
&
6
&
www.chemeurj.org
ꢁ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 0000, 00, 0 – 0
ÝÝ
These are not the final page numbers!

Organic–Inorganic Hybrid Supermicroporous Nanoparticles
FULL PAPER
phosphonate material HFeP-1-3 showed a high surface area
(556 m2 gÀ1) and uniform supermicropores of with dimen-
sions of about 1.1 nm. This hybrid phosphonate material can
be used as an efficient catalyst in the transesterification re-
action for the synthesis of several biodiesel compounds. The
supermicroporous nature of porosity can be used in shape-
selective catalytic reactions by tuning the organic scaffold in
the porous framework. Thus, this tiny nanomaterial
Scheme 2. The synthesis of porous iron phosphonate.
ACHTUNGTRENNUNG(3–5 nm) with its self-assembled nanostructure, mesophase,
and supermicroporosity can unveil a new dimension in the
synthesis of biofuels through environment friendly transes-
HFeP-1-4 by varying the L/M molar ratios to 2 and 4, respectively
(Scheme 2).
Instrumentation: Powder X-ray diffraction (PXRD) patterns were re-
corded by using a Bruker D8 Advance diffractometer operated at 40 kV
and 40 mA and calibrated with a standard silicon sample by using Ni-fil-
tered CuKa (l=0.15406 nm). Fourier-transform infrared (FT IR) spectra
of these materials were recorded by using a Nicolet MAGNA-FTIR 750
Spectrometer Series II. Elemental analyses were carried out by using a
Shimadzu AA-6300 atomic absorption spectrophotometer (AAS) fitted
with a double-beam monochromator and a Perkin–Elmer 2400 Series-II
CHN analyzer. A JEOL JEM 6700F field-emission scanning electron mi-
croscope (SEM) was used for the determination of the morphology of
the samples. The pore structure was determined by using a JEOL JEM
2010 transmission electron microscope (TEM) operated at an accelerat-
ing voltage of 200 kV. 1H and 13C NMR spectroscopy experiments were
carried out by using a Bruker DPX-300 NMR spectrometer. Thermogra-
vimetric analysis (TGA) and differential thermal analysis (DTA) of the
samples were carried out by using a TA-SDT Q-600 TGA thermal ana-
lyzer instrument under an air flow. Nitrogen adsorption/desorption iso-
therms were obtained by using a Beckman Coulter SA 3100 surface area
analyzer at 77 K at high vacuum.
terification reaction. Furthermore, these hybrid ironACHTUNTRGNEUNG(III)
phosphonate materials with internal porosity may also find
significant applications in drug delivery and as anode cells
in lithium ion batteries.
Experimental Section
Materials: Commercially available 1,3,5-tribromobenzene (98%), triethyl
phosphite (98%), and 1,3-diisopropylbenzene were purchased from
Sigma Aldrich. Anhydrous ironACTHNUGRTENUNG(III) chloride (96%) and nickel(II) chlor-
ide (99%) were purchased from E-Merck and Avra Chemicals, respec-
tively.
Synthesis of benzene-1,3,5-triphosphonic acid: 1,3,5-Tribromobenzene
(9.45 g) was dissolved in 1,3-diisopropylbenzene (75 mL) by heating at
1208C under a nitrogen atmosphere. Then the reaction mixture was
cooled to 708C and anhydrous nickel(II) bromide (1.5 g) was added to
the reaction mixture with vigorous stirring under inert atmosphere. The
reaction mixture was heated gradually to 1808C and triethyl phosphite
(22.5 mL) was added over 3 h. The heating was continued for another 6 h
at the same temperature under an inert atmosphere. Then the volatile
component with 1,3-diisopropylbenzene was distilled off and a dark vis-
cous residue was obtained. The hexaethyl-1,3,5-benzenetriphosphonate
was purified over a column of silica gel eluted with CHCl3 [CHCl3/
MeOH 10:1 v/v]. Colorless hexaethyl-1,3,5-benzenetriphosphonate was
obtained by solvent evaporation (yield: 5.85 g, 40%). The product ester
(4.5 g) was hydrolyzed with water (30 mL) in the presence of concentrat-
ed HCl (30 mL) for 12 h. The hydrolyzed solution was evaporated to dry-
ness and the residue was dissolved in distilled water (15 mL) and decolor-
ized with activated charcoal, then the filtrate was evaporated under re-
duced pressure to give benzene-1,3,5-triphosphonic acid (L)[23] as a white
solid (observed yield: 2.7 g, 92%). The compound was characterized by
using 1H, 13C, and 31P NMR spectroscopy and IR spectroscopy. 1H NMR
Transesterification reactions over HFeP-1-3: The hybrid supermicropo-
rous iron
ACHTUNGTREN(NUNG III) phosphonate nanoparticles were used as the heterogeneous
catalyst in a liquid-phase transesterification reaction (Scheme 3). The dif-
Scheme 3. Transesterification reaction catalyzed by HFeP-1-3.
ferent ethyl-substituted esters (10 mmol) were placed with methanol
(10 mL) in a 25 mL round-bottom flask fitted with a water-cooled con-
denser and the mixture was heated at 333 K. After 15 min, the catalyst
(1 wt% with respect to the reactant ester) was added to the mixture and
heating was continued for a further 6 h. The progress of the reaction was
monitored by using capillary gas chromatographic analysis (Agilent
4890D fitted with a HP-1 capillary column and a flame ionization detec-
tor). The catalyst was separated by a simple filtration technique, and the
reusability of the catalyst was confirmed through five successive catalytic
cycles with ethyl cyanoacetate as the representative ester under identical
reaction conditions.
(500 MHz, D2O): d=8.07 ppm (t, 3J
D2O): d=135.23, 136.07 ppm; 31P NMR (500 MHz, D2O): d=12.87 ppm;
IR (KBr): n˜ =3387, 3088, 2925, 2319, 1142, 1001, 943, 691, 536, 470 cmÀ1
Synthesis of porous iron(III) phosphonate HFeP-1-3: In a typical synthe-
sis of organic–inorganic hybrid supermicroporous iron(III) phosphonate,
(P,H)=15 Hz); 13C NMR (500 MHz,
ACHTUNGTRENNUNG
.
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
benzene-1,3,5-triphosphonic acid (L; 0.95 g, 3 mmol) was dissolved in dis-
tilled water (10 mL), then the pH of the solution was adjusted to around
4.0 by adding aqueous ammonia (12.5 wt% in water). In another beaker,
ironACHTUNGTRENNUNG(III) chloride (1.458 g, 9 mmol) was dissolved in distilled water
(10 mL). The synthetic gel was prepared by dropwise addition of the
phosphonic acid (L) source to the highly acidic (pHꢀ1) aqueous metal
salt solution, and the final pH of the gel was adjusted to 4.0–5.0 by fur-
ther addition of aqueous ammonia. The mixture was stirred overnight
and finally transferred to a Teflon-lined pressure vessel and kept at 453 K
for 1 d. The Teflon-lined autoclave was cooled to RT by decreasing the
temperature very slowly (108ChÀ1). The final mixture was centrifuged
and washed repeatedly with distilled water to collect the hybrid nanoma-
terial (HFeP-1-3). The final pH (ꢀ4.0) of the medium is acidic in nature
(yield=1.3 g). We synthesized two other samples, namely HFeP-1-2 and
Acknowledgements
A.B. wishes to thank DST, New Delhi, for providing instrumental facili-
ties through the DST Unit on Nanoscience at IACS. M.P. wishes to thank
CSIR, New Delhi, for a Senior Research Fellowship, and Sumanta Chat-
topadhyay for the Rietveld refinement of the powder XRD pattern.
Chem. Eur. J. 2013, 00, 0 – 0
ꢁ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
&
7
&
ÞÞ
These are not the final page numbers!

A. Bhaumik and M. Pramanik
[12] a) D. Chandra, A. Dutta, A. Bhaumik, Eur. J. Inorg. Chem. 2009,
4062–4068.
[1] a) M. Eddaoudi, J. Kim, N. Rosi, D. Vodak, J. Wachter, M.
OꢂKeeffe, O. M. Yaghi, Science 2002, 295, 469–472; b) P. M. Forster,
J. Eckert, J. S. Chang, S. E. Park, G. Ferey, A. K. Cheetham, J. Am.
Chem. Soc. 2003, 125, 1309–1312; c) M. Tiemann, Chem. Eur. J.
2007, 13, 8376–8388; d) R. Murugavel, A. Choudhury, M. G. Wala-
walkar, R. Pothiraja, C. N. R. Rao, Chem. Rev. 2008, 108, 3549–
3655; e) M. Nandi, M. Sarkar, K. Sarkar, A. Bhaumik, J. Phys.
Chem. C 2009, 113, 6839–6844; f) K. Sarkar, K. Dhara, M. Nandi, P.
Roy, A. Bhaumik, P. Banerjee, Adv. Funct. Mater. 2009, 19, 223–
234.
[2] a) M. E. Davis, Chem. Eur. J. 1997, 3, 1745–1750; b) H. Furukawa,
J. Kim, N. W. Ockwig, M. OꢂKeeffe, O. M. Yaghi, J. Am. Chem. Soc.
2008, 130, 11650–11661; c) J. X. Jiang, J. L. Jorda, M. J. Diaz-Caba-
nas, J. H. Yu, A. Corma, Angew. Chem. 2010, 122, 5106–5108;
Angew. Chem. Int. Ed. 2010, 49, 4986–4988; d) J. Seo, H. Sakamoto,
R. Matsuda, S. Kitagawa, J. Nanosci. Nanotechnol. 2010, 10, 3–20;
e) Q. R. Fang, D. Q. Yuan, J. Sculley, W. G. Lu, H. C. Zhou, Chem.
Commun. 2012, 48, 254–256; f) A. Almasoudi, R. Mokaya, J. Mater.
Chem. 2012, 22, 146–152.
[13] a) V. Valtchev, E. Balanzat, V. Mavrodinova, I. Diaz, J. E. Fallah,
J. M. Goupil, J. Am. Chem. Soc. 2011, 133, 18950–18956.
[14] a) Y. Zhai, Y. Dou, D. Zhao, P. F. Fulvio, R. T. Mayes, S. Dai, Adv.
Mater. 2011, 23, 4828–4850; b) B. Gong, Q. Peng, J. S. Jur, C. K.
Devine, K. Lee, G. N. Parsons, Chem. Mater. 2011, 23, 3476–3485.
[15] a) J. M. Kinsella, S. Ananda, J. S. Andrew, J. F. Grondek, M. P.
Chien, M. Scadeng, N. C. Gianneschi, E. Ruoslahti, M. J. Sailor,
Adv. Mater. 2011, 23, 248–253.
[16] a) R. Banerjee, H. Furukawa, D. Britt, C. Knobler, M. OꢂKeeffe,
O. M. Yaghi, J. Am. Chem. Soc. 2009, 131, 3875–3877; b) D. Chen,
L. Cao, F. Huang, P. Imperia, Y. B. Cheng, R. A. Caruso, J. Am.
Chem. Soc. 2010, 132, 4438–4444; c) H. R. Leea, T. Shibataa, M.
Kanezashia, T. Mizumob, J. Ohshitab, T. Tsuru, J. Membr. Sci. 2011,
383, 152–158.
[17] a) H. Baumann, M. Buhler, H. Fochem, F. Hirsinger, H. Zoebelein,
J. Falbe, Angew. Chem. 1988, 100, 41–62; Angew. Chem. Int. Ed.
Engl. 1988, 27, 41–62; <lit b>U. Biermann, U. Bornscheuer,
M. A. R. Meier, J. O. Metzger, H. J. Schaefer, Angew. Chem. 2011,
123, 3938–3956; Angew. Chem. Int. Ed. 2011, 50, 3854–3871;
c) P. M. Mortensena, J. D. Grunwaldta, P. A. Jensena, K. G. Knud-
senc, A. D. Jensena, Appl. Catal. A 2011, 407, 1–19; d) S. Dutta, S.
De, B. Saha, ChemPlusChem 2012, 77, 259–272.
[3] a) D. Chandra, B. K. Jena, C. R. Raj, A. Bhaumik, Chem. Mater.
2007, 19, 6290–6296; b) M. Nandi, R. Gangopadhyay, A. Bhaumik,
Microporous Mesoporous Mater. 2008, 109, 239–247; c) J. Schuster,
A. Keilbach, R. Koehn, M. Doeblinger, T. Doerfler, T. Dennen-
waldt, T. Bein, Chem. Eur. J. 2011, 17, 9463–9470; d) R. B. Restani,
V. G. Correia, V. D. B. Bonifcio, A. Aguiar-Ricardo, J. Supercrit.
Fluids 2010, 55, 333–339.
[18] a) V. Budarin, R. Luque, D. J. Macquarrie, J. H. Clark, Chem. Eur. J.
2007, 13, 6914–6919; b) H. J. Berchmans, S. Hirata, Bioresour. Tech-
nol. 2008, 99, 1716–1721.
[4] a) S. Inagaki, O. Ohtani, Y. Goto, K. Okamoto, M. Ikai, K. Yamana-
ka, T. Tani, T. Okada, Angew. Chem. 2009, 121, 4102–4106; Angew.
Chem. Int. Ed. 2009, 48, 4042–4046; b) W. Chaikittisilp, A. Suga-
wara, A. Shimojima, T. Okubo, Chem. Eur. J. 2010, 16, 6006–6014;
c) M. Waki, N. Mizoshita, Y. Maegawa, T. Hasegawa, T. Tani, T. Shi-
mada, S. Inagaki, Chem. Eur. J. 2012, 18, 1992–1998.
[5] a) D. Chandra, N. Mukherjee, A. Mondal, A. Bhaumik, J. Phys.
Chem. C 2008, 112, 8668–8674; b) B. G. Shpeizer, V. I. Bakhmoutov,
P. Zhang, A. V. Prosvirin, K. R. Dunbar, M. Thommes, A. Clear-
field, Colloids Surf. A 2010, 357, 105–115; c) A. K. L. Yuen, F. Hein-
roth, A. J. Ward, A. F. Masters, T. Maschmeyer, Microporous Meso-
porous Mater. 2012, 148, 62–72.
[6] a) G. B. Hix, V. Caignaert, J. M. Rueff, L. L. Pluart, J. E. Warren,
P. A. Jaffres, Cryst. Growth Des. 2007, 7, 208–211; b) D. Chandra,
M. W. Kasture, A. Bhaumik, Microporous Mesoporous Mater. 2008,
116, 204–209; c) J. F. Eubank, H. Mouttaki, A. J. Cairns, Y. Bel-
mabkhout, L. Wojtas, R. Luebke, M. Alkordi, M. Eddaoudi, J. Am.
Chem. Soc. 2011, 133, 14204–14207.
[19] a) S. R. Jagtap, Y. P. Patil, S. I. Fujita, M. Arai, B. M. Bhanage, Appl.
Catal. A 2008, 341, 133–138; b) V. Calabrꢃ, E. Ricca, M. G. D.
Paola, S. Curcio, G. Iorio, Bioprocess Biosyst. Eng. 2010, 33, 701–
710; c) J. M. Fraile, R. Mallada, J. A. Mayoral, M. Menꢄndez, L.
Roldꢅn, Chem. Eur. J. 2010, 16, 3296–3299.
[20] a) J. Otera, N. Dan-oh, H. Nozaki, J. Org. Chem. 1991, 56, 5307–
5311; b) V. T. Wyatt, M. J. Haas, J. Am. Oil Chem. Soc. 2009, 86,
1009–1016; c) R. Jothiramalingam, M. K. Wang, Ind. Eng. Chem.
Res. 2009, 48, 6162–6172; d) A. L. F. de Arriba, L. Simon, V. Alca-
zar, J. Cuellar, P. Lozano-Martinez, J. R. Moran, Adv. Synth. Catal.
2011, 353, 2681–2690.
[21] a) M. Di Serio, M. Ledda, M. Cozzolino, G. Minutillo, R. Tesser, E.
Santacesaria, Ind. Eng. Chem. Res. 2006, 45, 3009–3014.
[22] a) A. K. Patra, S. K. Das, A. Bhaumik, J. Mater. Chem. 2011, 21,
3925–3930.
[23] a) H. M. Rietveld, J. Appl. Crystallogr. 1969, 2, 65–71.
[24] a) L. Lutterotti, MAUD version 1.85, 2002, http://www.ing.unitn.it/~
maud/.
[7] a) J. Liang, G. K. H. Shimizu, Inorg. Chem. 2007, 46, 10449–10451;
b) S. H. Huang, C. H. Lin, W. C. Wu, S. L. Wang, Angew. Chem.
2009, 121, 6240–6243; Angew. Chem. Int. Ed. 2009, 48, 6124–6127.
[8] a) J. Kim, B. Chen, T. M. Reineke, H. Li, M. Eddaoudi, D. B. Moler,
M. OꢂKeeffe, O. M. Yaghi, J. Am. Chem. Soc. 2001, 123, 8239–8247.
[9] a) S. K. Ghosh, G. Savitha, P. K. Bharadwaj, Inorg. Chem. 2004, 43,
5495–5497; b) H. L. Gao, L. Yi, B. Ding, H. S. Wang, P. Cheng,
D. Z. Liao, S. P. Yan, Inorg. Chem. 2006, 45, 481–483; c) A. G.
Wong-Foy, O. Lebel, A. J. Matzger, J. Am. Chem. Soc. 2007, 129,
15740–15741; d) F. Q. Wang, W. H. Mu, X. J. Zheng, L. C. Li, D. C.
Fang, L. P. Jin, Inorg. Chem. 2008, 47, 5225–5233.
[25] a) W. He, W. Zhou, Y. Wang, X. Zhang, H. Zhao, Z. Li, S. Yan,
Mater. Sci. Eng. C 2009, 29, 1348–1350.
[26] a) D. Kong, J. Zon, J. Mcbee, A. Clearfield, Inorg. Chem. 2006, 45,
977–986.
[27] a) D. Zhao, D. Yuan, D. Sun, H. C. Zhou, J. Am. Chem. Soc. 2009,
131, 9186–9188; b) S. K. Das, M. K. Bhunia, M. M. Seikh, S. Dutta,
A. Bhaumik, Dalton Trans. 2011, 40, 2932–2939.
[28] a) M. Kruk, M. Jaroniec, Chem. Mater. 2001, 13, 3169–3183.
[29] a) P. I. Ravikovitch, A. V. Neimark, J. Phys. Chem. B 2001, 105,
6817–6823.
[30] a) P. B. Venuto, Microporous Mater. 1994, 2, 297–411; b) M. Ranoc-
chiari, J. A. van Bokhoven, Phys. Chem. Chem. Phys. 2011, 13,
6388–6396.
[31] a) N. Pal, M. Paul, A. Bhaumik, J. Solid State Chem. 2011, 184,
1805–1812.
[10] a) P. M. Digiacomo, M. B. Dines, Polyhedron 1982, 1, 61–68; b) G.
Cao, H. Lee, V. M. Lynch, T. E. Mallouk, Solid State Ionics 1988, 26,
63–69; c) K. J. Frink, R. C. Wang, J. L. Colbn, A. Clearfield, Inorg.
Chem. 1991, 30, 1438–1441.
[11] a) A. Subbiah, D. Pyle, A. Rowland, J. Huang, R. A. Narayanan, P.
Thiyagarajan, J. Zon, A. Clearfield, J. Am. Chem. Soc. 2005, 127,
10826–10827; b) E. Brunet, C. Cerro, O. Juanes, J. C. Rodriguez-
Ubis, A. Clearfield, J. Mater. Sci. 2008, 43, 1155–1158; c) S. S. Ire-
monger, J. Liang, R. Vaidhyanathan, I. Martens, G. K. H. Shimizu,
Thomas, D. Daff, M. Z. Aghaji, S. Yeganegi, T. K. Woo, J. Am.
Chem. Soc. 2011, 133, 20048–20051.
[32] a) B. S. Balaji, M. Sasidharan, R. Kumar, B. Chanda, Chem.
Commun. 1996, 707–708; b) C. Camacho-Camacho, M. Biesemans,
M. V. Poeck, F. A. G. Mercier, R. Willem, K. Darriet-Jambert, B.
Jousseaume, T. Toupance, U. Schneider, U. Gerigk, Chem. Eur. J.
2005, 11, 2455–2461.
Received: January 14, 2013
Published online: && &&, 0000
&
8
&
www.chemeurj.org
ꢁ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 0000, 00, 0 – 0
ÝÝ
These are not the final page numbers!

Organic–Inorganic Hybrid Supermicroporous Nanoparticles
FULL PAPER
Iron brews biofuels: Highly crystalline,
supermicroporous ironACTHUNTGRNEUNG(III) phospho-
Nanomaterials
nate nanoparticles have been synthe-
sized through a hydrothermal reaction
between benzene-1,3,5-triphosphonic
acid and FeCl3. The resulting material
was used as an efficient and recyclable
catalyst for the synthesis of biofuels
under mild reaction conditions (see
scheme).
M. Pramanik, A. Bhaumik* &&&& — &&&&
Organic–Inorganic Hybrid Super-
ACHUTNGRENmNUG icroporous IronHCATUNGTREN(NUGN III) Phosphonate
Nanoparticles as an Efficient Catalyst
for the Synthesis of Biofuels
Chem. Eur. J. 2013, 00, 0 – 0
ꢁ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
&
9
&
ÞÞ
These are not the final page numbers!