Lanthanide carboxylate frameworks: Efficient heterogeneous catalytic system for epoxidation of olefins

Article abstract of DOI:10.1007/s10562-011-0731-y

Two lanthanide-based three dimensional metal-organic frameworks (MOF) viz. [Nd(HCOO)₃]_n (1) and [Pr(HCOO)₃]_n (2) have been synthesized and characterized. Both the compounds have similar structure. In this study we have demonstrated that the compounds are highly efficient in catalyzing epoxidation of various cyclic and linear olefinic substrates. MOF compounds are stable and recyclable under the reaction conditions. Notably, MOF systems are remarkably more active and selective than the corresponding lanthanide oxide in epoxidation reaction of olefins.

Full text of DOI:10.1007/s10562-011-0731-y

Catal Lett (2012) 142:124–130
DOI 10.1007/s10562-011-0731-y
Lanthanide Carboxylate Frameworks: Efficient Heterogeneous
Catalytic System for Epoxidation of Olefins
Rupam Sen
•
Debraj Saha Subratanath Koner
•
Received: 1 July 2011 / Accepted: 31 October 2011 / Published online: 15 November 2011
Ó Springer Science+Business Media, LLC 2011
Abstract Two lanthanide-based three dimensional
metal–organic frameworks (MOF) viz. [Nd(HCOO) ] (1)
and [Pr(HCOO) ] (2) have been synthesized and charac-
material scientists, and physical scientists for their appli-
cation potential in the field of catalysis [1], gas adsorption
and separation [2], storage [3], artificial nucleases for the
hydrolytic cleavage of DNA and RNA [4], contrast agents
for magnetic resonance imaging [5] as well as magnetic
materials [6]. Apart from naturally occurring porous
materials and recently developed micro/mesoporous
materials [7, 8] (SBA-15, MCM-41 etc.) or phosphate
systems [9], hydrothermally synthesized tunable micropo-
rous MOFs are of great interest for their structural flexi-
bility, diversity and spatial control. Microporous MOFs
with tunable channel structures can have great potentials
for the direct incorporation of catalytic sites with desirable
activity [10]. Therefore, rational designing of microporous
MOFs for selective catalytic activity has remained a
challenge.
3
n
3
n
terized. Both the compounds have similar structure. In this
study we have demonstrated that the compounds are highly
efficient in catalyzing epoxidation of various cyclic and
linear olefinic substrates. MOF compounds are stable and
recyclable under the reaction conditions. Notably, MOF
systems are remarkably more active and selective than the
corresponding lanthanide oxide in epoxidation reaction of
olefins.
Keywords Metal–organic framework ꢀ Lanthanide ꢀ
Epoxidation ꢀ Olefin ꢀ Heterogeneous catalysis
1
Introduction
A variety of reactions have been studied using MOF
catalyst. Metal centers have direct relevance in showing
catalytic activity by MOFs. The active center might be
either isolated metal ions or clusters [11, 12] (dimers [13],
trimers [14], tetramers [15] etc.), chains [16], or sheets
[17] connected through the organic linkers. Vitorino
et al. [18] showed the successful use of lanthanide
metal–organic frameworks as Ziegler–Natta Catalysts for
the Selective Polymerization of Isoprene. Hupp and
co-workers [19] obtained oxidation of olefins catalyzed by
a bimetallic mixed ligand MOF in heterogeneous condi-
tion using substituted iodosylbenzene oxidant. In this
compound the active center is a Schiff base Mn(III)
Porous framework solids are increasingly attracting atten-
tion in recent time because of their fascinating and tunable
porosity and molecular topologies. These materials have
attracted a major share of attention of the chemists,
Electronic supplementary material The online version of this
article (doi:10.1007/s10562-011-0731-y) contains supplementary
material, which is available to authorized users.
R. Sen ꢀ D. Saha ꢀ S. Koner (&)
Department of Chemistry, Jadavpur University,
Kolkata 700 032, India
moiety which is stacked in paddle-wheel carboxylate Zn2
e-mail: snkoner@chemistry.jdvu.ac.in
0
dimers and 4,4 -biphenyldicarboxylate ligands forming
Present Address:
R. Sen
Department of Chemistry,
CICECO, University of Aveiro, 3810-193 Aveiro,
Portugal
square planar layers. Iron(III)-based MOF containing
benzene 1,3,5-tricarboxylate, Fe(III)-MIL100, with zeo-
type architecture has been synthesized hydrothermally
[20]. Friedel–Crafts reaction of benzene with benzyl
1
23

Lanthanide Carboxylate Frameworks: Efficient Heterogeneous Catalytic System
125
chloride was catalyzed by Fe(III)-MIL100 at 343 K and
showed an excellent selectivity of diphenylmethane. Ravon
et al. [21] have successfully used zinc dicarboxylate MOF
solids as heterogeneous catalysts for the alkylation of aro-
matics. Alkylation of toluene with tert-butyl-chloride
affords the corresponding para-substituted product selec-
Aldrich and were used as received and solvents were
purchased from Merck (India). The solvents were distilled
and dried before use.
Fourier transform infrared spectra (in KBr) were
measured on a Perkin–Elmer RX I FT-IR spectrometer.
Elemental analyses (CHN) were performed using a Perkin–
Elmer 240 elemental analyzer. The powder X-ray diffrac-
tion (XRD) patterns of the samples were recorded with a
Scintag XDS-2000 diffractometer using CuKa radiation.
The products of the catalytic reactions were identified and
quantified by a Varian CP-3800 gas chromatograph using a
CP-Sil 8 CB capillary column.
tively. The same reaction catalyzed by AlCl or the acidic
3
zeolite beta gives mixtures of ortho- and para-substituted
compounds and dialkylated products. Recently, Garcia and
co-workers [22] added a new example of aerobic oxidation
of benzylic alcohol catalyzed by Cu (BTC) (where, BTC:
3
2
1
,3,5-benzenetricarboxylate) MOF.
Oxidative transformations [23] especially epoxidation of
alkenes are the key chemical processes in biology [24],
synthetic organic chemistry, and in the chemical industry
2.2 Synthesis and Characterization
[
25]. In recent years, considerable advances have been
Although the complexes were reported earlier [32], we
have synthesized the materials with some modification.
Previously Gao and co-workers [32] prepared these
made in the development of atom-efficient catalytic oxi-
dation employing tert-butyl hydroperoxide (tert-BuOOH)
[
26]. The by-product, tert-BuOH generated from tert-butyl-
compounds hydrothermally by mixing LaCl and lactic
3
hydroperoxide can be separated by distillation or recycled
for other industrial production, for example, methyl tert-
butyl ether (MTBE). There is an ever-growing interest in
the application of reusable catalysis for the synthesis of fine
chemicals, including enantioselective reactions [27], which
could reduce the large amounts of waste products often
formed in non-catalytic organic synthesis. Recently we
have succeeded to use layered metal carboxylates and
hydrogenphosphate to catalyze olefin epoxidation reaction
in heterogeneous condition [28, 29]. Two dimensional
layered metal–carboxylates having a space between layers
acid in aqueous solution using (Et) N as base, but in our
3
case we prepared the compounds [Nd(HCOO) ] (1) and
3
n
[Pr(HCOO) ] (2) solvothermally. For digestion, Nd(NO )
3 3
3
n
and formic acid were added in the molar ratio of 1:2 in
10 ml of DMF and kept at 180 °C for 3 days followed by
slow cooling at the rate of 5 °C/h to room temperature. The
crystals thus formed were filtered off, washed first with
water and then with a small amount of ethyl alcohol and
dried in air. Compound 2 was prepared in a similar manner
by using Pr(NO ) instead of Nd(NO ) with the same
3
3
3 3
molecular ratio of reactants as that of neodymium ana-
logue. Yield ca. 65 and 68% (based on metal) for 1 and 2,
respectively. For preliminary characterization of the com-
pounds, elemental analysis and IR spectroscopic study
were undertaken. Anal. Calcd. for [Nd(HCOO) ] 1; C =
˚
of about 3 A, can be used as heterogeneous catalyst in
olefin epoxidation reaction instead of intercalating metal
complex into layers of the clay or LDH type materials [28].
Layered V–P–O compound is also found to be useful in
olefin epoxidation reaction [29]. Further, Lanthanide-based
MOFs are being used in catalytic oxidation of organic
sulfur compounds as well as alkanes [30]. However, reports
of using lanthanide carboxylate in heterogeneous catalytic
epoxidation of olefins are still very scarce [31].
3
n
12.9, H = 1.0, found C = 12.5, H = 1.1%; Selected IR
-
1
-
peaks (KBr disk, cm ): 1579 [t (CO )], 1433, 1401 [ts
as
2
-
(CO2 )], 1338 [t (C–O)], and 3500–3200 [t(O–H); s. br].
s
Anal. Calcd. for [Pr(HCOO) ] 2; C = 12.8, H = 1.0,
3
found C = 12.5, H = 1.1%; Selected IR peaks (KBr disk,
-
1
-
-
Here, we wish to report the synthesis and use as heter-
ogeneous epoxidation catalysts of two lanthanide carbox-
ylate framework [Ln(HCOO) ] (where Ln = Nd/Pr).
cm ): 1610 [tas (CO2 )], 1442, 1398 [t (CO )], 1321
s
2
[t (C–O)], and 3500–3200 [t(O–H); s. br].
s
3
n
2.3 General Procedure for Epoxidation Reaction
2
Experimental
The catalytic reactions were carried out in a glass batch
reactor. Substrate, solvent and finely powdered catalysts
were first mixed. The mixture was then equilibrated to
2
.1 Materials and Methods
70 °C in an oil bath. After addition of tert-BuOOH, the
Neodymium nitrate hexahydrate, praseodymium nitrate
hexahydrate, formic acid, cyclopentene, cyclooctene,
cyclododecene, 1-hexene, 1-octene, 1-decene, styrene,
reaction mixture was stirred continuously for 24 h. The
products of the epoxidation reactions were collected at
different time intervals and were identified and quantified
by gas chromatography. Compounds were dried under
vacuum (*100 °C, 12 h) prior to use it as catalyst.
3-Me styrene, 4-Me styrene, trans-stilbene and tert-butyl-
hydroperoxide (70 wt% aqueous) were purchased from
123

1
26
R. Sen et al.
3
Results and Discussion
3
.1 Structure of [Nd(HCOO) ] (1) and [Pr(HCOO) ]
3 n
3
n
(
2)
Although the structures of the compounds have been
reported previously [32], we redetermined the crystal
structures of compounds 1 and 2 only to verify the integrity
of the compounds. X-ray studies reveal that compounds 1
3
?
and 2 have identical structure. Each Ln ion possesses a
distorted tricapped trigonal prismatic environment sur-
rounded by nine oxygen atoms from nine different formate
anions. Each formate anion acts as l
bridge and coor-
,1,3
1
3
dinates to three different Ln ions. The distance between
?
˚
the l1,1-bridged metal ions is in the range of around 4.0 A,
where distance between the other metal ions are in the
˚
range of 6 A. Packing diagram of the compounds 1 and 2
Fig. 2 Plot showing nitrogen sorption isotherm of compound 1. Inset
shows the pore-size distribution of compound 1
demonstrates that three-dimensional arrangement afforded
equilateral triangular pores in compounds in the solid state
3.3 Catalytic Epoxidation Reactions
(
Fig. 1). The dimension of pores is *5.30 9 5.30 9
˚
.30 A for both the compounds.
5
Olefin epoxidation reactions catalyzed by lanthanide con-
taining homogeneous catalysts are well documented [33].
Homogeneous catalysts, however, suffer from the prob-
lems of recycling of the catalyst as the separation of cat-
alyst from reaction mixture is often impossible. Recycling
of catalysts is a task of great economic and environmental
advantages in chemical and pharmaceutical industry,
especially when expensive and/or toxic heavy metal
complexes are employed. To this end many attempts have
been made, such as intercalating or encapsulating the
metal complex into the layered compounds or within
the cavities of a porous solid (e.g., zeolites) [34], binding
the metal complex into the polymeric matrix [35], and
employing the steric hindrance [36] to design recyclable
catalysts. Polymer supported lanthanide-binol systems and
3
.2 Nitrogen Sorption Studies
The nitrogen sorption measurements of the compounds
were undertaken to verify porous nature of the compounds
as well as to calculate the surface area of the catalyst. BET
(Brunauer–Emmett–Teller) surface area of 1 was calcu-
lated from the N adsorption isotherms. The adsorption and
2
desorption isotherms of 1 are shown in Fig. 2. The
adsorption of N follows a type III isotherm with a surface
2
2
-1
area (SBET) equal to 11 m g . Nitrogen sorption mea-
surement also afforded the pore size distribution of the
porous compound. This corroborates the information
obtained from X-ray crystallographic analysis as regards
the porous nature of the compounds. As the structure of the
two compounds is identical only compound 1 was sub-
jected for nitrogen sorption study.
Ln(O-iPr) systems have been extensively used in catalytic
3
oxidation of olefinic substrates [37]. Nevertheless, in this
study porous lanthanide carboxylates have been used as
such, instead of using any support, as recyclable hetero-
geneous catalyst in olefin epoxidation. The results of the
catalytic epoxidation of different substrates are summa-
rized in Table 1. The kinetic profiles of the progress of the
reactions using the catalysts 1 and 2 are shown in Figs. 3
and 4, respectively. The overall catalytic efficacy of 1 and
2
in epoxidation reactions were complete for less bulky
olefinic substrates (Table 1). The epoxidation of cyclo-
pentene proceeded smoothly, showing good conversion to
their epoxides with 100% selectivity. The oxidation of
cyclooctene also goes smoothly, showing conversion (78
and 86%, for 1 and 2, respectively) to form cyclooctene
oxide with 100% selectivity, while the conversion of bulky
cyclododecene was not complete with the conversion up to
69% simultaneously producing the side product, In case of
Fig. 1 Packing diagram showing porous structure of the compound 1
1
23

Lanthanide Carboxylate Frameworks: Efficient Heterogeneous Catalytic System
127
Table 1 Epoxidation of olefins catalyzed by 1 and 2
Entry
Substrate
Reaction time/h
Conversion [wt%]
% Yield of products
TON
Epoxide
Others
1
2
3
9
24
24
a)
b)
98
99
98
99
–
–
2,014
2,008
a)
b)
78
86
78
86
–
–
976
1,066
a
31
a)
b)
61
69
30
34
506
566
a
35
b
b
4
5
24
24
a)
b)
89
91
51
54
38
37
1,180
1,192
c
24
a)
b)
82
86
58
63
958
994
c
23
d
d
6
7
24
24
a)
b)
78
83
55
57
23
26
910
958
a)
b)
53
51
53
51
–
–
406
386
8
9
24
24
24
a)
b)
a)
b)
a)
b)
99
98
48
42
42
38
99
98
48
42
22
25
–
–
–
1,616
1,606
664
–
622
e
20
1
0
410
e
13
482
(
a), (b) corresponds to the catalytic performance of compounds 1 and 2, respectively. Reaction conditions: alkenes (1 g); catalyst (2 mg); tert-
BuOOH (2 mL); acetonitrile (8 mL); Temperature 65–68 °C. The products of the epoxidation reactions were collected at different time intervals
and were identified and quantified by Varian CP-3800 gas chromatograph equipped with an FID detector and a CP-Sil 8 CB capillary column
Turn over number (TON) moles converted/moles of active site
a
b
Cyclododecanol; Benzaldehyde; 3-Me-benzaldehyde; 4-Me-benzaldehyde; Decanone
c
d
e
linear alkenes, 1-hexene shows almost complete conver-
sion and producing epoxide as the sole product, but in case
of long chain alkenes the conversion was not complete
like the earlier linear alkenes; the conversion only limited
to 38–42% for 1-octene and 1-decene (Table 1). On the
other hand, oxidation of styrene showed 89–91% conver-
sion while epoxide yields were 51–54%. Along with
styrene oxide, benzaldehyde is also formed. In fact, in the
epoxidation of styrene with tert-BuOOH over transition
metal immobilized zeolite or molecular-sieves catalysts,
epoxide yield seldom exceeds 40% [38]. In our recent
attempt we have succeeded to improve the yield of styrene
epoxide up to *70% using layered transition metal car-
boxylate catalysts [28]. The substituted styrene was also
123

1
28
R. Sen et al.
and 2. The best performance of the catalysts is observed in
case of tert-BuOOH in the acetonitrile medium. Hydrogen
peroxide and sodium hypochlorite solution were less
effective for the conversion (Table 2). Alkyl-hydroperox-
ides are used on a large scale in industrial epoxidation, for
example, in Halcon–Arco and Sumitomo processes [39,
40]. The recycling of co-products, e.g., tert-BuOH has
been realized in the Sumitomo process. Besides, to
ascertain the catalytic efficacy of compounds 1 and 2 we
have undertaken few control experiments. Temperature
dependence of catalytic performance of compounds 1 and
2
has been studied. While catalysts showed almost no
conversion at room temperature they exhibit the desired
conversion at 70 °C demonstrating the vital role of tem-
perature on the activation of the catalyst. Further, com-
parison of catalytic efficiency of 1 and 2 with the
corresponding heterogeneous non-porous lanthanide oxide
catalysts clearly indicates that the lanthanide carboxylate
MOFs perform as much superior catalyst than the metal
oxides (Table 3).
Fig. 3 Kinetic profile for epoxidation of olefins catalyzed by
compound 1
3.4 Separation, Catalyst Reuse and Heterogeneity Test
The major advantage of the use of heterogeneous catalysts
is to recover the catalyst from the reaction mixtures by
simple filtration and recycle. To test if metal is leached out
from the solid catalyst during reaction, the liquid phase of
the reaction mixture is collected by filtration at the reaction
temperature after 30% of the epoxidation reaction is
completed and the residual activity of the supernatant
solution after separation of the catalysts was studied. The
impending leaching was premeditated as, the organic phase
of a first run was separated from the catalyst and new
reagents were added to the clear filtrate, and the compo-
sition of the reaction mixture was determined by GC. This
homogeneous reaction mixture was treated as a standard
catalytic experiment. After 6 h, the composition was
determined, and no reaction was observed, which excludes
the presence of active species in solution. In order to check
the stability of the catalysts, we have characterized the
solids after the completion of reactions. Besides, to test if
metal ions are leaching out of the catalyst, the reaction
mixture was filtered out after the reaction and was sub-
jected to atomic absorption spectroscopic analysis. The
analysis showed the absence of metal ions in the filtrate.
These experiments clearly demonstrate that metal is not
leaching out from the solid catalyst during epoxidation
reactions. After the catalytic reactions are over, solid cat-
alyst was recovered by centrifugation and washed with
fresh acetonitrile several times and dried in air oven. The
recovered catalyst was then subjected for X-ray powder
diffraction analysis. Comparison of X-ray diffraction pat-
terns of the virgin catalysts and recovered catalysts
Fig. 4 Kinetic profile for epoxidation of olefins catalyzed by
compound 2
converted 86% successfully with oxide selectivity up to
6
3% and the other products were found as their corre-
sponding aldehyde. Here, trans-stilbene was also subjected
for epoxidation, but the conversion was not inspiring,
although oxide was the unique product. Evidently, as the
bulkiness of the cyclic olefins and chain length of the
linear alkenes is increasing the conversion and turnover
numbers are gradually diminishing in the epoxidation
reactions catalyzed by catalysts 1 and 2. Selectivity and
conversion becomes less when the bulkiness or chain
length of the substrates is increased which may be
explained on the basis of steric hindrance causes by the
substrates. When the substrate is bulky steric hindrance
prevents itself in approaching towards active site with
ease. Consequently, the conversion is lowered in catalytic
reactions.
The catalytic reactions were performed employing
varieties of oxidants to study the catalytic efficacy of 1
1
23

Lanthanide Carboxylate Frameworks: Efficient Heterogeneous Catalytic System
129
Table 2 Epoxidation of alkenes using variety of oxidants catalyzed by 1 and 2
a
Substrate
Oxidant
Reaction time/h
Conversion [wt%]
% Yield of products
Epoxide
Others
b
H
2
O
2
9
9
55 (58)
16 (19)
39 (32)
6 (5)
16 (26)
b
NaOCl
10 (14)
c
H
2
O
2
24
24
48 (41)
14 (15)
35 (31)
14 (15)
13 (10)
–
NaOCl
Reaction conditions were the same as given in footnote of Table 1
a
b
Values in parenthesis show the results obtained for complex 2; Cyclopentanone; 1-hexanone
c
Table 3 Epoxidation of alkenes catalyzed by metal oxides
Table 4 Catalytic efficacy of the recovered compounds 1 and 2 in
successive runs in cyclopentene epoxidation
Substrate Reaction time/h Conversion % Yield of products
wt%]
[
Compounds
Cycles
Conversion
wt%)
Yield of
product
TON
Epoxide
Others
(
(
wt%)
Cyclopentene
a
Nd
Pr
2
O
3
9
9
17
21
2
15
1
2
First reuse
99
98
97
99
99
97
99
97
97
98
98
97
2,014
1,974
1,965
1,988
1,988
1,975
2
O
3
21
–
Second reuse
Third reuse
First reuse
Cyclododecene
b
Nd
Pr
2
O
3
9
9
15
14
6
5
9
b
2
O
3
9
Second reuse
Third reuse
Reaction conditions were the same as given in footnote of Table 1
a
b
Cyclopentanone; Cyclododecanol
Reaction conditions were the same as given in footnote of Table 1
Acknowledgments We acknowledge the Department of Science
and Technology (DST), Government of India for funding a project (to
SK) (SR/S1/IC-01/2009). We also thank DST for funding the
Department of Chemistry, Jadavpur University to procure a single
crystal X-ray facility under DST-FIST programme.
convincingly demonstrate that the structural integrity of the
compounds 1 and 2 is remained unaltered after the epoxi-
dation reactions (see Supplementary Data Figs. S1, S2).
Notably the recovered catalyst can be reused in epoxidation
reactions for several times with no considerable loss of
activity (Table 4). The kinetic profiles of the epoxidation
reaction of cyclopentene using virgin and recovered cata-
lysts are virtually remained the same (see Supplementary
Data Figs. S3, S4).
References
1
2
3
. Podkolzin SG, Stangland EE, Jones ME, Peringer E, Lercher JA
2007) J Am Chem Soc 129:2569
. Pan L, Adams KM, Hernandez HE, Wang X, Zheng C, Hattori Y,
Kaneko K (2003) J Am Chem Soc 125:3062
. Luo J, Xu H, Liu Y, Zhao Y, Daemen LL, Brown C, Timofeeva
TV, Ma S, Zhou HC (2008) J Am Chem Soc 130:9626 and
references therein
(
4
Conclusion
To summarize, we have demonstrated that the lanthanide
carboxylate frameworks can be used as selective catalyst
for the epoxidation of a variety of olefins using tert-butyl-
hydroperoxide. The frameworks behaved as the heteroge-
neous catalyst, can be easily recovered after reaction by
filtration and washing and subsequently be used without
having significant deactivation of catalyst due to either
leaching of active species or degradation of the structure.
The catalyst shows excellent efficiency towards epoxida-
tion reactions as reflected in high selectivity in epoxides
and high turnover number of the reactions. Further inves-
tigations employing this type of catalyst in other reactions
are currently in progress in our laboratory.
4
5
. Komiyama M, Takeda N, Shigekawa H (1999) Chem Commun
443
. Messerle L, Nolting D, Bolinger L, Stolpen AH, Mullan BF,
Swenson D, Madsen M (2005) Acad Radiol 12:S46
1
6. Sweet LE, Roy LE, Meng F, Hughbanks T (2006) J Am Chem
Soc 128:10193
7
8
. Celer EB, Jaroniec M (2006) J Am Chem Soc 128:14408
. Kresge CT, Leonowicz ME, Roth WJ, Vartuli JC, Beck JS (1992)
Nature 359:710
9. Jhung SH, Leea JH, Cheetham AK, F e´ rey G, Chang JS (2006) J
Catal 239:97
0. Fujita M, Kwon YJ, Washizu S, Ogura K (1994) J Am Chem Soc
116:1151
1. Tranchemontagne DJ, Mendoza-Cortes JL, Okeeffe M, Yaghi
OM (2009) Chem Soc Rev 38:1257
1
1
`
´
123

1
30
R. Sen et al.
1
1
1
1
1
1
1
1
2
2. Chizallet C, Lazare S, Bazer-Bachi D, Bonnier F, Lecocq V,
Soyer E, Quoineaud A, Bats N (2010) J Am Chem Soc 132:12365
3. Chui SSY, Lo SMF, Charmant JPH, Orpen AG, Williams ID
26. Br e´ geault JM (2003) Dalton Trans 3289
27. Blaser HU, Pugin B (1995) In: Jannes G, Dubois V (eds) Chiral
reactions in heterogeneous catalysis. Plenum, New York, p 33
28. Sen R, Bhunia S, Mal D, Koner S, Miyashita Y, Okamoto KI
(2009) Langmuir 25:13667
29. Sen R, Bera R, Bhattacharjee A, G u¨ tlich P, Ghosh S, Mukherjee
AK, Koner S (2008) Langmuir 24:5970
30. G a´ ndara F, Puebla EG, Iglesias M, Proserpio DM, Snejko N,
Monge A (2009) Chem Mater 21:655
31. Sen R, Koner S, Hazra DK, Helliwell M, Mukherjee M (2011)
Eur J Inorg Chem 241
32. Lin JM, Guan YF, Wang DY, Dong W, Wang XT, Gao S (2008)
Dalton Trans 6165
33. Xia QH, Ge HQ, Ye CP, Liu ZM, Su KX (2005) Chem Rev
105:1603
34. Medina JC, Gabriunas N, Paez-Mozo E (1997) J Mol Catal A:
Chem 115:233
35. Anzenbacher PJ, Kral V, Jursikova K, Gunterova J, Kasal A
(1997) J Mol Catal A: Chem 118:63
(1999) Science 283:1148
4. Seo JS, Whang D, Lee H, Jun SI, Oh J, Jeon YJ, Kim K (2000)
Nature 404:982
`
5. Li H, Eddaoudi M, Okeeffe M, Yaghi OM (1999) Nature
4
02:L276
6. Dybtsev DN, Nuzhdin AL, Chun H, Bryliakov KP, Talsi EP,
Fedin VP, Kim K (2006) Angew Chem Int Ed 45:916
7. Gomez-Lor B, Gutierrez-Puebla E, Iglesias M, Monge MA,
Ruiz-Valero C, Snejko N (2002) Inorg Chem 41:2429
8. Vitorino MJ, Devic T, Tromp M, F e´ rey G, Visseaux M (2009)
Macromol Chem Phys 210:1923
9. Cho SH, Ma B, Nguyen ST, Hupp JT, Albrecht-Schmitt TE
(2006) Chem Commun 2563
0. Horcajada P, Surbl e´ S, Serre C, Hong DY, Seo YK, Chang JS,
Gren e` che JM, Margiolakid I, F e´ rey G (2007) Chem Commun
2
820
2
2
2
1. Ravon U, Domine ME, Gaudillere C, Desmartin-Chomel A,
Farrusseng D (2008) New J Chem 32:937
2. Dhakshinamoorthy A, Alvaro M, Garcia H (2011) ACS Catal
36. Bhyrappa P, Young JK, Moore JS, Suslick KS (1996) J Mol Catal
A: Chem 113:109
37. Sasai H, Suzuki T, Itoh N, Tanaka K, Date T, Okamura K,
Shibasaki M (1993) J Am Chem Soc 115:10372
38. Vos DED, Dams M, Sels BF, Jacobs PA (2002) Chem Rev
102:3615
1
:48
3. Jiang T, Persson AKA, Backvall JE (2004) In: Backvall JE (ed)
Modern oxidation methods. Wiley-VCH, Weinheim
4. Wu AJ, Penner-Hahn JE, Pecoraro VL (2004) Chem Rev 104:903
5. Brinksma J, de Boer JW, Hage R, Feringa BL (2004) In: B a¨ ckvall
JE (ed) Modern oxidation methods, Ch. 10. Wiley-VCH,
Weinheim, p 295
2
2
39. Sheng MN, Zajaczek GJ (1968) ARCO, U.K. Patent 1 136 923
40. Halcon Kollar J (1967) U.S. Patent 3 350 422
1
23