Improved photocatalytic activity in a surfactant-assisted synthesized Ti-containing MOF photocatalyst under blue LED irradiation

Article abstract of DOI:10.1039/c4nj01536c

The Ti-incorporated metal-organic framework structure, MIL-125, its amine-functionalized form, MIL-NH₂ and its surfactant-assisted version, SMIL-NH₂ were synthesized via a solvothermal route. The samples were characterized by XRD, SEM, EDS, UV-vis spectroscopy, and N₂ adsorption-desorption measurements. In the presence of a nonionic surfactant, cylindrical SMIL-NH₂, with 50-250 nm particle size, was obtained. The photocatalytic properties of the materials were evaluated by deoximation reaction. Compared with MIL-NH₂, the nanostructured SMIL-NH₂ MOF has more than double the surface area and is able to catalyze the regeneration of carbonyl compounds from various oximes at twice the rate in an energy-efficient photocatalytic system. Furthermore, it has been successfully shown that this new nanostructured photocatalyst is significantly durable under the reaction conditions and can be easily recycled after the reaction, with significant retention of its photocatalytic activity.

Full text of DOI:10.1039/c4nj01536c

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Improved photocatalytic activity in a surfactant-
assisted synthesized Ti-containing MOF
photocatalyst under blue LED irradiation†
Cite this:DOI: 10.1039/c4nj01536c
Sedigheh Abedi and Ali Morsali*
The Ti-incorporated metal–organic framework structure, MIL-125, its amine-functionalized form, MIL-NH
and its surfactant-assisted version, SMIL-NH were synthesized via a solvothermal route. The samples were
characterized by XRD, SEM, EDS, UV-vis spectroscopy, and N adsorption–desorption measurements. In
the presence of a nonionic surfactant, cylindrical SMIL-NH , with 50–250 nm particle size, was obtained.
The photocatalytic properties of the materials were evaluated by deoximation reaction. Compared with
MIL-NH , the nanostructured SMIL-NH MOF has more than double the surface area and is able to
2
2
2
2
Received (in Montpellier, France)
9th September 2014,
2
2
Accepted 5th November 2014
catalyze the regeneration of carbonyl compounds from various oximes at twice the rate in an energy-
efficient photocatalytic system. Furthermore, it has been successfully shown that this new nanostructured
photocatalyst is significantly durable under the reaction conditions and can be easily recycled after the
reaction, with significant retention of its photocatalytic activity.
DOI: 10.1039/c4nj01536c
www.rsc.org/njc
1
8–20
been developed.
The porous channels in MOF structures
Introduction
can be used as photocatalysis sites. Theoretical calculations
Today, the rapid everyday rise of waste associated with fossil show that MOFs are semiconductors or insulators with band
fuels is one of the major concerns of ecologists. On the other gaps between 1.0 and 5.5 eV, which can be altered by changing
2
1
hand, the rapid reduction in fossil sources of energy has led the the degree of conjugation in the ligands. Experimental results
attention of many enthusiasts to developing ways of utilizing show that the band gaps of IRMOF-type samples can be tuned
carbon-neutral energy sources. Extensive efforts have been by varying the functionality of the linker.2
2
made to replace these kinds of nonrenewable sources with
Among numerous scientific attempts to investigate the
widely available, abundant solar energy. Photocatalytic systems unexplored catalytic properties of crystalline MOFs,7,23–30 the
are one the most promising routes to achieve this worthy global development of robust MOFs with the potential for photo-
objective. Among them, heterogeneous photocatalytic systems, catalytic conversion of light energy into chemical energy has
using the most widely used TiO
2
-based photocatalysts, have had only limited success. A few investigations have been made
attracted much attention, due to their biological and chemical into their application in the photocatalytic degradation of
1
–3
9,31
inertness as well nontoxic and inexpensive characteristics.
organic compounds.
Garcia and coworkers revealed the
The unique and tunable architectural properties of metal– semiconductor behaviour of MOF-5 and showed the potential
organic frameworks (MOFs) have made them promising candidates performance of this MOF in the photocatalyzed degradation of
4
,5
32
for heterogeneous catalysis applications. The extraordinarily high phenol in aqueous solutions. The development of special
surface areas, porosities and well-defined pore structures of these photocatalytic systems for selective organic transformations is
materials are the cause of recent demands for their use as a further step in this field that has been more rarely investi-
6
–8
catalysts.
applications in light harvesting
catalytic reactions such as H production,
and carbon dioxide reduction, in gas separation and storage phosphorescent [Ir (ppy) (dcbpy)]Cl and [Ru (bpy) (dcbpy)]Cl
2
Recently, a variety of modified MOFs and their gated. Very recently, this barrier has been broken using MOFs
9
–12
, in driving various photo- containing other co-catalysis species, such as metal complex parti-
1
3–15
16
2
O
2
production,
cles. Lin’s group used functionalized dicarboxylic UiO-67 containing
1
7
III
II
2
2
0
and in the catalytic transformation of organic molecules, have (where ppy is 2-phenylpyridine and bpy is 2,2 -bipyridine) in
three photocatalytic organic transformations (the aza-Henry
Department of Chemistry, Faculty of Sciences, Tarbiat Modares University,
reaction, aerobic amine coupling, and aerobic oxidation of
P.O. Box 14115-4838, Tehran, Iran. E-mail: morsali_a@modares.ac.ir;
3
3
thioanisole). A visible-light responsive Ti-based MOF photo-
catalyst (Ti-MOF-NH ) with 1.5 wt% Pt deposited into it was
also used for the photocatalytic reduction of nitrobenzene
Fax: +98 21 8009730; Tel: +98 21 82884416
Electronic supplementary information (ESI) available. See DOI: 10.1039/
c4nj01536c
†
2
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under visible-light irradiation. The co-catalytic role of the Pt ionization detector (FID). NMR spectra were recorded on a
particles was revealed by ESR measurement and, with optimum Bruker 250 MHz spectrometer.
amounts of Pt deposited in Ti-MOF-NH , the reduction reaction
2
was carried out successfully within 70 h under visible light Synthesis of MOF structures
3
4
irradiation.
Synthesis of MIL-125 and MIL-NH
2 8 8 4
. MIL-125, or Ti O (OH) -
To our knowledge, there are no reports of using visible-light
responsive MOF materials without any additives in selective
organic transformations. Since morphology-controlled synthesis
of porous materials is very important for their adsorption,
[
O C–C H –CO ] , and MIL-NH were prepared according to the
2
6
4
2 6
2
38
solvothermal methods reported by Serre et al. and Matsuoka
et al. respectively. Typically, a mixture of terephthalic acid, or
H
(
stainless-steel autoclave and heated for 48 h at 423 K under
autogenous pressure. Back at room temperature, the white
solid was recovered by filtration, washed twice with DMF and
dried under air at 80 1C. The free solvent was removed by
calcination at 200 1C overnight for 12 hours. MIL-NH2 was
synthesized in a similar way with H BDC-NH instead of H BDC.
39
2
BDC, (3 mmol, 498 mg), 2 mmol of TPOT (0.6 ml), DMF
3
5,36
separation, and catalytic selectivity,
in this study the changes
9 ml), and methanol (1.0 ml) was transferred to a Teflon-lined
in the structural properties of the Ti-based MOF photocatalyst,
MIL-NH , which is an amine-functionalized version of MIL-125,
2
prepared by the conventional solvothermal method have been
compared with those of the same MOF after surfactant-assisted
solvothermal synthesis. Fortunately we could expose the visible
light photocatalytic activity of the resultant Ti-based MOF photo-
2
2
2
2
catalyst (Ti-MOF-NH ) in the regeneration of carbonyl com-
2
Synthesis of SMIL-NH . This structure was synthesized
pounds from oximes (deoximation reaction) in very mild
photoreaction conditions under blue LED light irradiation.
It will be revealed that the Ti-containing MOF structure synthe-
sized in the presence of a nonionic amphiphilic surfactant,
Pluronic P123, has a more uniform cylindrical morphology with
39
according to a known procedure with a little modification.
In a typical experiment, 2.0 g of Pluronic P123 (Aldrich, average
M D 5800), was dissolved in 40 ml of DMF at room temperature.
w
The mixture was stirred magnetically, dissolving the surfactant
completely and was subsequently sonicated for 15 minutes. Then,
2
50–250 nm particle size and more than double the surface area
mmol (0.6 ml) of TPOT and 3 mmol (0.54 g) of H BDC-NH were
2 2
of that synthesised by the conventional solvothermal method,
and that it can consequently catalyze the regeneration of carbonyl
compounds from various oximes in an energy-efficient photo-
catalytic system. Furthermore, we will successfully show that this
nanostructured catalyst is significantly stable under the reaction
conditions and can be easily recycled after the reaction, retaining
its photocatalytic reactivity.
added rapidly and the mixture was stirred at 35 1C for 5 h under
an Ar atmosphere. Then, for the aging process, the reaction
mixture was kept at 140 1C without stirring for 48 hours. The
mixture was cooled to room temperature and the resultant
yellow solid was filtered off, washed thoroughly with DMF and
dried in air at 80 1C. Both the free solvent and the surfactant
molecules were removed by calcination at 200 1C overnight
for 12 hours.
Experimental section
Photocatalytic reaction using the photocatalytic system
Materials
A mixture of oxime (20 mg) and catalyst (30 mg) in dry CH CN
3
(
10 ml) was prepared in a two-necked flask. One neck was used
Poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) tri-
block copolymer template (EO PO EO , Pluronic P123 from
for the oxygen inlet and outlet and the other was equipped with
a condenser with a bladder at the end. The flask was filled with
pure oxygen, and sonicated for 5 minutes. Subsequently, it was
irradiated under blue LED lamps (4 ꢀ 3 W). Then the catalyst
was filtered off through a 0.4 mm filter and the reaction mixture
was analyzed using gas chromatography.
After the reactions of different oximes, the catalyst was
collected by centrifugation, stirred in 1 : 1 CH CN : CH OH for
2
20
70
20
Aldrich), 2-amino-benzenedicarboxylic acid (H BDC-NH ; C H NO
4
2
2
8
7
from Aldrich), 1,4-benzenedicarboxylic acid (H
Merck), tetrapropyl orthotitanate (TPOT; Ti-(OC
Aldrich), N,N-dimethylformamide (DMF, from DAE JUNG
Reagents Chemicals), and methanol (CH OH) were used with-
out additional purification. CH CN (from Merck) was distilled
2
BDC; C
8
H
6
O
4
, from
3
7 4
H ) , from
3
3
and dried by refluxing in the presence of sodium hydride under
an argon atmosphere and kept on 4 Å molecular sieves.
3
3
4 hours and then dried in an oven at 75 1C and denoted as
3
7
SMIL-NH R.
All oximes were synthesized according to known procedures
2
from the corresponding carbonyl compounds (from Merck), and
were characterized by nuclear magnetic resonance spectroscopy
1
13
Results and discussion
(
H-NMR and C-NMR spectra; see the ESI†).
After the synthesis of MIL-125 (or Ti
and MIL-NH2 according to the known procedures,
Powder X-ray diffraction (PXRD) data were acquired on a Philips surfactant-assisted synthesized MIL-NH , denoted as SMIL-NH ,
8 8 4 2 6 4 2 6
O (OH) [O C–C H –CO ] )
Instrumentation
38,39
the
2
2
X-Pert diffractometer using Cu Ka radiation. SEM images were was prepared using a solvothermal method in the presence of
captured on a Philips XL-300 instrument. The nitrogen sorption a nonionic structure-directing agent, Pluronic P123. The powder
isotherms were collected on a Belsorp (BELMAX, Japan). The GC XRD pattern recorded for the synthesized MIL-125 control
analyses were performed on an Echrom A90 using a flame sample matches with the literature and the pattern simulated
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Fig. 2 SEM images of solvothermally synthesized MIL-NH
and surfactant-assisted synthesized SMIL-NH , (c) and (d).
2
, (a) and (b),
2
particle size decrease and morphology alteration observed in
the presence of P123 is a result of competition between the
6
+
surfactant and the ligand for coordination to Ti sites in this
medium, instead of the surfactant being assembled to make
micelles and play its usual templating role in the solution. Very
recently, we showed that in the presence of the same concen-
tration of P123 in DMF solvent, but with copper salt and BDC
ligand, the precursors of the HKUST-1 structure, the template
Fig. 1 Powder XRD patterns: (a) simulated from X-ray data of MIL-125
2 2 2
single crystal, (b) MIL-NH , (c) SMIL-NH , (d) MIL-125, (e) SMIL-NH R.
4
2
based on the X-ray data of the MIL-125 single crystal (Fig. 1a and d). effect of the nonionic surfactant directed the final structure.
The major diffraction pattern is assigned to the rhombohedral The typical octahedral morphology of the crystals remained
structure. In addition, a comparison of the simulated MIL-125 intact while some new ordered domains were constructed
single crystal and experimental powder X-ray diffraction patterns of within the original framework. Here, the existence of the
6
+
both the synthesized MIL-NH
sized structure, which is named SMIL-NH
structure estimated from the basic crystallographic data (Fig. 1a–c). for dictating the final MOF structure. A comparison of N
As Fig. 2 shows, SEM images of MIL-NH and SMIL-NH indicate adsorption–desorption analysis of MIL-NH2 and SMIL-NH2
2
and the surfactant-assisted synthe- oxophilic Ti metal centers in the relatively harsh conditions
2
, confirmed the parent of the solvothermal reactor makes a completely different path
2
2
2
that in the presence of the nonionic block copolymer, Pluronic clearly verified this statement (Fig. 3). As shown in Fig. 3a,
P123, the angular plate structures of MIL-NH , with nonuniform the hysteresis loop in the N adsorption–desorption isotherm of
crystal sizes between 400 and 1000 nm, clearly convert into the MIL-NH indicates a type IV mesoporous material, and this has
soft plate structures of SMIL-NH , with smaller crystals of about completely disappeared in the isotherm of SMIL-NH , which
0–250 nm. Moreover, more uniform cylindrical structures shows a type I isotherm, characteristic of microporous materials.
2
2
2
2
2
5
have been constructed from the surfactant-assisted synthesis This observation that is quite the opposite of what was seen in
system. Recently, the effect of the surfactant-assisted medium the case of HKUST-1, evidently proving the discrepancy of the
on the morphology and particle size of [Cu (btc) ], known as surfactant role in the two cases.
3
2
4
0
HKUST-1 has been studied. As has been well demonstrated,
To investigate the photocatalytic activity of MIL-NH and its
2
in the presence of the cationic surfactant CTAB in aqueous surfactant-assisted synthesized analogue, SMIL-NH
2
, regenera-
3
ꢁ
solution, the triethylammonium salt of the BTC ligand, btc , is tion of carbonyl compounds from oximes, or the deoximation
+
surrounded by CTA species. Therefore, in the presence of reaction, was chosen as a probe. This is a useful organic
higher amounts of CTAB as an additive, nucleation is retarded transformation because of its use in the purification and
significantly, which causes a larger particle size for the final characterization of carbonyl compounds and also its importance
4
3–47
crystals. In contrast, it has been shown that via common routes in organic synthesis.
This reaction has proceeded in crystal-
of MOF synthesis in organic solvents, increased concentration line TiO -based photocatalytic systems under UV and also solar
2
8,49
4
of additives leads to smaller crystal size, due to suppression of light.
Recently, a new binary photocatalyst system including
It seems that in the presence of the nonionic a periodic mesoporous organosilicate (PMO) decorated with
surfactant P123, in DMF as a solvent, controlled particle amorphous TiO was developed for the deoximation reaction
formation of carboxylic acid-based MOFs in solution generally of various types of aldoximes and ketoximes under sunlight
4
0,41
crystal growth.
2
4
1
50
occurs and this affects the ultimate crystal size. However, the irradiation. Nowadays, the quest for the use of high photon
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Fig. 4 Yield-versus-time profiles of the deoximation reaction in the
presence of (a) MIL-NH
2 2
, (b) SMIL-NH and (c) Degussa P25; y-axis: yield
of acetophenone in %, x-axis: time in hours.
Table 1 Lattice parameters of MIL-NH
2
structures prepared in the
absence or presence of P123
a
2
ꢁ1
b
c
c
3
ꢁ1
Sample
S
BET (m g ) Dmicro (nm) Dmeso (nm) Vmeso (cm g
)
MIL-NH
SMIL-NH
SMIL-NH
2
566
1132
1066
0.7
0.6
0.6
3.3
2.4
2.4
0.179
0.151
0.151
2
d
2
R
Fig. 3 (a) N
2
adsorption–desorption analysis and (b) BJH analysis of
and SMIL-NH
a
b
The Brunauer–Emmett–Teller (BET) surface area. The micropore
c
MIL-NH
2
, SMIL-NH
2
2
.
size distributions were calculated using an MP plot. The mesopore
volume and the mesopore size distributions were calculated using the
d
Barrett–Joyner–Halenda (BJH) method. The recycled catalyst.
efficiency, low voltage of electricity, and high power stability LED
5
1
lamps as a light source has attracted wide attention, owing to Here the nonionic surfactant, P123, acts as a capping agent
their simplified practical aspects as well from the standpoint of instead of being assembled, making micelles and acting as
environmental and economic concerns for cleaner and cheaper scaffold for construction of the MOF structure. The discrepancy
5
2–55
organic transformations.
2
Fortunately, both MIL-NH and may be due to the different affinities of the two metal centers,
SMIL-NH could successfully catalyze the deoximation reaction copper and titanium ions, to the hydrophilic head groups of the
2
of acetophenone oxime in the presence of blue LED lamps (4 ꢀ 3 W) surfactant in the organic solution.
under an oxygen atmosphere. At the beginning of the reaction,
No change was observed in the absence of irradiation,
when the oxime concentration is high, in the presence of either catalyst or oxygen for runs carried out under the same experi-
MIL-NH or SMIL-NH the rate of acetophenone production is mental conditions (Table 2, entry 2). Since no reaction took
2
2
the same (Fig. 4). Interestingly, after 4 h, the concentration place in the presence of MIL-125 as a catalyst (Table 2, entry 3)
curves for the product formation with respect to time begin to even after 48 h irradiation, the role of the amine-functionalized
separate and the rate of product formation with SMIL-NH
2
is versions of the MIL can be described as an antenna effect.
about twice as fast as that with MIL-NH . Lattice parameters of UV-vis spectra of MIL-NH and SMIL-NH are shown in Fig. 5.
2
2
2
the two structures have been provided in Table 1. As these For both structures, the major absorption edge is similar and in
clearly show, and as is confirmed by the N adsorption– the visible light region extends to around 500 nm, relative to the
desorption analysis, MIL-NH and SMIL-NH are entirely dis- 350 nm absorption edge reported for MIL-125. The observed
similar in pore size distribution and eventually in their surface distinction is known to be induced by O–Ti ligand-to-metal
areas. While MIL-NH has a 3.3 nm average mesopore size and charge transfer in TiO (OH) inorganic clusters, apparently
a 566 m g surface area, SMIL-NH has a smaller pore size of influenced by H BDC being replaced with H
.4 nm and a larger surface area of 1132 m g , which is more Therefore, the antenna role of the amine-functionalized MILs
2
2
2
2
5
2
ꢁ1
6,8
2
2
2 2
BDC-NH .
2
ꢁ1
2
than two times that of the former. Although the fact that both in the photocatalytic deoximation reaction of oximes in an
reactions have the same induction period needs more precise oxygen atmosphere can be described as in Scheme 1. In this
investigation, the improved lattice parameters may be one of known manner, an electron and a hole are generated from light
the reasons for the higher catalytic activity of SMIL-NH
In confirmation of the SEM results, these data evidently are respectively.
in contrast with the previous results reported for HKUST-1.
2
.
excitation, and transfer to the oxygen and oxime molecules,
Moreover, a Ti-leaching test has been per-
formed after a 10 h reaction of acetophenone oxime under blue
7
,56–58
4
2
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Table 2 Regeneration of carbonyl compounds from oximes in blue LED
light irradiation using SMIL-NH
2
a
Time Yield
Entry Substrate
Product
(h)
(%)
1
2
10
100
b
c
4
12
8
—
100
d
3
48
—
2 2
Fig. 5 UV-vis spectra of (a) MIL-NH and (b) SMIL-NH .
4
5
6
6
100
4
4
.5
.5
100
86
e
48
48
57
74
2
Scheme 1 The antenna role of MIL-NH in transferring the generated
7
electron and hole to the oxygen and oxime molecules during light
excitation.
LED light irradiation. The ICP analysis of the reaction solution
showed that no Ti species has been leached, which validates the
stability of the MOF structure as well as the heterogeneous
character of our catalytic system.
8
9
24
24
100
100
2
The remarkable photocatalytic activity of SMIL-NH in such
mild reaction conditions encouraged us to examine its photo-
catalytic ability for other structurally diverse oximes. Since photo-
catalytic deoximation has been known to proceed via a cationic
intermediate formed via the reaction of the oxime substrate with
49
photogenerated holes,
activated ketoximes with electron-
1
0
1
48
48
33
38
donating substituents such as methyl and methoxy were equally
well converted into the corresponding ketones in relatively short
times under mild reaction conditions (Table 2, entries 4 and 5).
Very recently, a deoximation reaction of 4-methoxyacetophenone
oxime to the corresponding ketone in the presence of C–N
codoped sonofabricated crystalline titania (anatase) as well as a
sample of bicrystalline framework titania, (anatase/brookite,
1
a
GC yield, reaction conditions: oxime (20 mg), catalyst (30 mg), 10 ml dry
b
CH
3
CN, O
2
atmosphere (1 atm), blue LED light (4 ꢀ 3 W lamps). In the
5
9
dark, in the absence of O
2
and/or catalyst the same results were obtained. 78/22) was examined under blue LED irradiation. In similar
c
d
In the presence of the recycled catalyst, SMIL-NH
2
R. In the presence
reaction conditions to our photocatalytic system, with the
former catalyst the reaction proceeded quantitatively within 2 h,
e
of MIL-125 as a catalyst. In the presence of P25 as a catalyst.
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2 2
whereas just 31 percent of the corresponding carbonyl compound decrease in the surface area of SMIL-NH R relative to SMIL-NH
was obtained with the latter catalyst. With the most reactive does not affect its activity, which is still greater than that of
commercial crystalline TiO , Degussa P25 (anatase/rutile, 75/25), MIL-NH2.
2
86 percent of 4-methoxyacetophenone was obtained in the same
reaction conditions mentioned in Table 2, in comparison with
a quantitative amount of the product formed in the presence of
Conclusion
2
SMIL-NH within 4.5 h irradiation (Table 2, entry 5). It is worth
We succeeded in the preparation of a new morphology of
MIL-NH in the presence of Pluronic P123, as a structure-
2
directing agent and in solvothermal conditions. Adsorption–
desorption isotherm, BET, and SEM analyses clearly established
the effectiveness of the procedure for the synthesis of uniform
mentioning that there is no report of the deoximation reaction
with MOFs in such mild reaction conditions. Moreover, the
crystalline structure of these materials is completely different
and there are no diffraction peaks of any TiO crystalline phase
2
(anatase, rutile or brookite) in their structure. Meanwhile,
2
cylindrical SMIL-NH nanoparticles possessing double the surface
after 48 h irradiation, deactivated oximes containing electron
withdrawing groups such as 4-chloroacetophenone oxime,
area of MIL-NH , with 50–250 nm particle sizes. Furthermore,
2
regeneration of carbonyl compounds from various oximes in an
energy-efficient photocatalytic system was successfully catalyzed
3-bromoacetophenone oxime and the more passive substrate,
methyl 2-pyridyl ketone oxime gave weak to moderate yields of
the corresponding carbonyl products (Table 2, entries 6, 7 and 11).
Furthermore, the reaction of sterically hindered oxime substrates
proceeded over a long time and was not completed in the case of
deactivated substrates such as (4-chlorophenyl)(phenyl)methanone
oxime (Table 2, entries 9 and 10). This observation shows the
preference of the substrate to pass into the channels of the
2
by this stable nanostructured photocatalyst in an O atmosphere
and under blue LED light irradiation. In addition, it was shown
that this nanostructured MOF catalyst is stable in the reaction
conditions and can be easily recycled after the reaction, retaining
its photocatalytic reactivity.
photoactive MOF framework rather than to react on the surface. Acknowledgements
In other words, the reaction proceeds within the channels of
the MOF framework.
This work was supported by Tarbiat Modares University.
For practical purposes, recycling of the catalyst is an important
problem to solve. Considering the potential application of
Notes and references
SMIL-NH , we collected the catalyst used in the deoximation
2
reactions of diverse substrates, thoroughly washed it with 1 : 1 of
1 A. Mills and S. Le Hunte, J. Photochem. Photobiol., A, 1997,
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2 N. J. Peill, L. Bourne and M. R. Hoffmann, J. Photochem.
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CH
for 12 h. A powder XRD pattern of this recycled catalyst, denoted
as SMIL-NH R, is shown in Fig. 1e, and obviously indicates that
3
CN and MeOH, and subsequently dried it in an oven at 80 1C
2
the crystallinity of the MOF structure has been reduced slightly,
while the original XRD pattern of the structure remains intact and
matches with the X-ray data of the MIL-125 single crystal. The
deoximation reaction of acetophenone oxime in the presence of
3 M. R. Hoffmann, S. T. Martin, W. Choi and D. W. Bahnemann,
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SMIL-NH R in the same optimum conditions mentioned in
2
Table 2 gave a quantitative yield of acetophenone after 12 h
irradiation (Table 2, entry 2). SEM images of SMIL-NH R before
2
and after washing the catalyst, shown in Fig. S1 (ESI†), not only
verify the importance and effectiveness of the washing stage to
disconnect the agglomerated particles of the MOF structure
formed during the reaction, but also confirm the basic morpho-
logy remains nearly intact after the deoximation reaction. In
addition, some residual nitrogen content (about 7%) seen in
the energy dispersive X-ray analysis (EDS) of the unwashed
catalyst, which has been eliminated in the EDS analysis of
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2
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SMIL-NH
the porosity parameters shown in Table 1 shows that just a little
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2
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