Catal Lett (2015) 145:589–595 DOI 10.1007/s10562-014-1433-z
An Efficient Catalyst Based on a Metal Metalloporphyrinic Framework for Highly Selective Oxidation Weijie Zhang • Pingping Jiang • Ying Wang Jian Zhang • Pingbo Zhang
•
Received: 24 August 2014 / Accepted: 9 November 2014 / Published online: 19 November 2014 Ó Springer Science+Business Media New York 2014
Abstract An efficient metal–organic framework catalyst was developed with manganese tetrakis(4-carboxyphenyl)porphyrin as either bridging moiety or catalytically active sites under a hydrothermal condition. Surprisingly, the X-ray diffraction details showed that this porous network, MMPF (MMPF denotes iron-connected metal metalloporphyrinic framework) was successfully constructed with a physically flexible framework and resistance to basic solution. Accordingly, catalytic studies have demonstrated that MMPF can catalyze the selective oxidation of a variety of substrates with PhIO as oxidant in acetonitrile solution under mild temperature. More importantly, the MMPF outperformed the homogeneous Mn-TPP in catalyzing epoxidation of cyclohexene, mainly due to its high efficiency of 3D network-based nanochannel-reactor in MMPF. This gave rise to a structural resistance to formation of catalytically inactive species. Keywords Metal–organic framework Biomimetic catalysis Selective oxidation Porphyrin
Electronic supplementary material The online version of this article (doi:10.1007/s10562-014-1433-z) contains supplementary material, which is available to authorized users. W. Zhang P. Jiang (&) Y. Wang P. Zhang The Key Laboratory of Food Colloids and Biotechnology, Ministry of Education, School of Chemical and Material Engineering, Jiangnan University, Wuxi 214122, China e-mail:
[email protected] J. Zhang School of Chemistry and Environmental Science, Lanzhou City University, Lanzhou 730000, China
1 Introduction Metalloporphyrins are well known for a remarkable class of candidate materials with a range of applications, such as light harvesting, oxygen transportation and catalysis [1–3]. Due to their excellent catalytic performance and high product selectivity, synthetic metalloporphyrins have been utilized in epoxidation to mimic cytochrome P450 as biomimetic catalyst in the last decade. However, the application of metalloporphyrins as catalyst in solution is usually challenging because of the formation of catalytically inactive dimers and fast degradation in homogeneous catalysis [4]. Metal–organic frameworks (MOFs) constructed from organic bridging ligands and metal ions/clusters constitute an outstanding and steadily expanding group of porous crystalline materials [5–9]. In terms of catalytic functions, MOFs have been successfully projected to bridge the gap between heterogeneous materials and enzymes. To date, several MMPFs with uncoordinated metalloporphyrinbased building synthons, including carboxylic acid groups or pyridyl moieties, have been applied to mimic properties of cytochrome P450 [10–16]. Indeed, this will bring an advantage that these metalloporphyrinic MOFs (MMPFs) can be considered as self-supported catalysts with an enhanced performance, due to their high-density active sites into frameworks. Therefore, this motivated us to use MMPF approach to target efficient heterogeneous catalysts with open coordination frameworks, which is essential to catalysis application. Noteworthy, most MMPFs based on divalent cations (especially M2? = Cu, Zn, Co and Cd) are often less stable than those based on trivalent and more charged cations (M3? = Al, Fe, Cr, M4? = Ti, Zr), especially regarding to hydrolysis [17–19]. Among them, recent studies have
123
590
shown that for a given carboxylate linker, the Fe ion as node is a candidate in MOFs because of its low toxicity [20], redox potential [21, 22] and rich coordination geometries [21–24]. Nevertheless, the Fe ion exhibits a tendency to undergo hydrolysis to afford hydrated iron oxides, making it difficult to obtain a desirable crystalline coordination network in pure phase. Only a few Fe-based MOFs (MIL-141 (A), A = Li, Na, K, Rb, Cs within the pores) built from porphyrinic linkers, and even fewer reports on their catalytic properties have been investigated so far [25]. Herein, we reported a novel metal metalloporphyrinic framework catalyst, namely MMPF, based upon Mn-TCPP (TCPP = tetrakis(4-carboxyphenyl)porphyrin) as a bridging ligand and Fe as metal ion under hydrothermal condition. The new compound, MMPF (MMPF denotes ironbased metalloporphyrinic metal organic framework) was successfully constructed with a stable 3D framework. The resulting purple block crystals were washed and obtained. Interestingly, a solvent-induced breathing effect of MMPF has been founded by a detailed XRD study. Simultaneously, MMPFs showed an unprecedented high robustness not only in boiling water but also in basic aqueous solutions with pH values in the range of 7–12. Moreover, a range of substrates have been employed as substrates to investigate catalytic efficiency of MMPF.
2 Experimental 2.1 Materials and Reagents Methyl 4-formylbenzoate, fresh distilled pyrrole, propionic acid, N,N-dimethylformamide (DMF), iron(II) chloride tetrahydrate (FeCl24H2O), manganese(II) chloride tetrahydrate (MnCl24H2O). All commercial chemicals were used without further purification unless otherwise mentioned. 2.2 The Porphyrin Synthesis The 5, 10, 15, 20-tetrakis(4-carboxyphenyl)porphyrin (H2TCPP) was synthesized by the modified Lindsey method [26], involving NaOH hydrolysis of the corresponding intermediate. Thus, 1.22 g (7.46 mmol) of 4-carbomethoxybenzaldehyde and 0.50 g of distilled pyrrole (7.46 mmol) were added to 750 mL of dry CH2Cl2 for 30 min. Then, BF3 etherate (92 uL) was added via syringe, and the reaction mixture was protected from light. After stirring at room temperature for 1 h, 1.37 g (5.62 mmol) of p-chloranil was added in the solid form and the solution was stirred overnight. The solution was concentrated to a small volume
123
W. Zhang et al.
using a rotary evaporator. To this solution, silica gel (60–200 mesh) was added and the slurry was evaporated to give a dry black powder, which was loaded on a silica column using CHCl3. First CHCl3 fraction removed any poly (pyrrole) impurity and the porphyrin was eluted with 2–4 % acetone in CHCl3. It was then further purified by recrystallization from a 1:4 CHCl3/methanol mixture (v/v). Yield: 0.55 g (35 %). 1H NMR (400 MHz, CDCl3) d 9.08–8.64 (m, 8H), 8.62–8.37 (m, 8H), 8.39–8.13 (m, 8H), 4.34–3.88 (m, 12H), –2.79 (s, 2H). A solution of H2TCPP 0.42 g (0.50 mmol) and MnCl24H2O (0.24 g, 1.00 mmol) in 50 mL of DMF was refluxed for 12 h. After the mixture was cooled to room temperature, 500 mL of H2O was added. The resultant precipitate was filtered and washed with 200 mL of H2O for three times. The obtained solid was dissolved in CHCl3, followed by washing three times with water. The organic layer was dried over anhydrous magnesium sulfate and evaporated to afford quantitative dark green crystals [27]. In the next stage, 0.45 g (0.50 mmol) of the latter product was dissolved in 20 mL of THF. To this, 1.60 g of NaOH in 20 mL of water was added and the solution was stirred at room temperature for 3 days. At the end of this period, THF was removed by rotary evaporation. The crude porphyrin was treated with 20 mL of 2 N HCl solutions, yielding a green precipitate, which was filtered, washed with water, and dried. Protonated porphyrin was neutralized by adding 10 mL of pyridine and subsequently removed by vacuum distillation. Then, purple solid was washed with water and dried under a vacuum. Yield: 0.39 g (88 %). 2.3 Synthesis of MMPF FeCl34H2O (2.0 mg, 0.01 mmol) and Mn-TCPP (8.8 mg 0.01 mmol) in 5 mL of DMF were ultrasonically dissolved in a 25 mL Pyrex vial. The mixture was heated in 150 °C oven for 72 h. After cooling down to room temperature, purple block shaped crystals were harvested by filtration (6 mg, 60 % yield). As synthesized samples of MMPF were dispersed onto a glass plate for imaging. The crystals of MMPF were shown to be cubic in morphology with sizes from 25 to 50 lm (Fig. S1). Crystallographic data have been deposited with the Cambridge Crystallographic Data Centre: CCDC 941505, this data can be obtained free of charge from The Cambridge Crystallographic Data Center via www.ccdc.cam.ac.uk/data_request/cif. It should be mentioned that the catalyst was used as prepared. 2.4 Stability Measurements for MMPF Experimental details of stability test: pH 0, pH 2, pH 4, pH 7, pH 10 and pH 12 aqueous solutions were prepared.
Efficient Catalyst Based on MMPF
Then, 50 mg of sample was soaked in each solution and also in boiling water for 1 day. After that, all the samples are centrifuged and the filtrates are kept. Samples soaked in the acidic aqueous solutions (ligand is insoluble in acidic aqueous solution, while soluble in basic solution), and then they were taken pictures (Fig. S2). 2.5 Catalytic Activity Test Biomimetic epoxidation studies: Olefin (500 mM), PhIO (10 mM), catalyst (5 mM), acetonitrile (5.0 mL) and bromobenzene 50 mg as internal standard sealed in a Teflonlined screw cap vial were stirred at room temperature. This epoxidation procedure was routinely employed according to previous literatures with a minor modification [28–30]. For other substrates, similar assays were performed. Thereafter, conversion and selectivity were determined by GC using an SE-54 column (50 °C for 1 min, then 10 °C min-1 up to 140 °C and 140 °C for 15 min) based on the conversion of oxidant rather than olefins. To be more precise, the progress of the reaction was monitored by GC with internal standard method, by taking a small sample of the reaction mixture and centrifugation. The product selectivity was defined as follows (epoxide as an example): Epoxide selectivity = GC peak area of epoxide/RGC peak area of all products 9 100 %. In addition, the data of catalytic performance were an average of at least three measurements. A standard deviation of ±4 % has to be considered on average for the conversion and selectivity.
3 Results and Discussion 3.1 Characterization of MMPF MMPF crystallized in the monoclinic P12/c1(13) space group (Table 1). It contains manganese (III) tetra (p-carboxyphenyl) porphyrins (Fig. 1a) and a bridging bent trinuclear iron cluster (Fig. 1b). Each trinuclear cluster is coordinated by eight separate Mn-TCPP carboxylate moieties; each Mn-TCPP carboxylate coordinates four distinct Fe(III) trinuclear clusters. Compared with ever iron cluster in MOFs [22–24], this bent trinuclear iron cluster has not been presented in existing MOF structures. In the overall ˚ 9 9A ˚ and network of MMPF, there are alternating 5A ˚ 9 8A ˚ pores down the crystallographic an axis and 7A ˚ 9 5A ˚ pores down the c axis. Calculations using the 3A PLATON program indicated that the total volume of MMPF was 47.3 % occupied by solvent molecules, which would provide a potential micro-environment for catalysis. It should be mentioned here that, the samples being heated at 150 °C after a solvent exchange with methanol was the standard for activation throughout the experiments, in order
591 Table 1 Crystal data and structure refinements for Fe-MMOF Formula
C96H48Fe3Mn2N8O18
Fw
1,878.85
Color
purple
Crystal system
monoclinic
Space group ˚) a (A
14.908 (6)
P12/c1 (13)
˚) b (A ˚) c (A
15.345 (6)
a, c (8)
90
b (8) ˚ 3) V (A
b = 90.424 (6)
Z dcalcd.(g/cm3)
2 0.982791
l (mm-1)
0.579
T (K)
173 (2)
F (000)
1,904
27.753 (11)
6,348.69 (400)
Reflns collected
35,928
Independent reflns
11,276
Obsd data [I [ 2r (I)]
5,501
Data/restraints/parameters
11,276/0/573
Completeness
11,276
GOF on F2
1.039
R1, wR2 [I [ 2r (I)]
0.0555,0.1313
R1, wR2 (all data)
0.1039,0.1223
to remove the guest molecules, like DMF. By heating at 150 °C, the high temperature phases were stable after cooling down again to room temperature. Of further significance, the solvent-induced breathing effect of MMPF has also been demonstrated after being immersed in different solvents (Fig. 2), which may lead to the difference on XPD pattern. MOFs with a breathing behaviour combine ‘‘regularity’’ with ‘‘softness’’ by exhibiting large, reversible structural deformations (softness) without loss of crystallinity or bond breaking. A recent research revealed that, expanding and shrinking of the pores within the coordination networks is concomitant with the removal and addition of coordinated solvent [25, 31]. In particular, the peak value moved to a higher angle region, which was indicative of an expansion in structure. A remarkable cell volume reduction was observed upon removal of free and coordinated DMF ligands from the as-prepared framework without cleavage of any coordination bonding. Another interesting phenomenon was observed that the pores within MMPF shrank when being reimmersed in some other solvents, like CHCl3 (Fig. 2). The aforementioned test provides a fundamental understanding of this heterogeneous catalyst. On the other hand, most MOFs are more or less sensitive to moisture, which could be one of the key limitations to
123
592
W. Zhang et al.
Fig. 1 a Mn-TCPP (TCPP = tetrakis(4carboxyphenyl)porphyrin) as a bridging ligand; b Bridging bent trinuclear iron cluster in MMPF (Fe atoms: purple, Mn atoms: green, O atoms: red, C atoms: gray); c The MMPF network viewed along the crystallographic a-axis; d The MMPF network viewed along the crystallographic c-axis
Methanol DMAc CHCl 3 Re-acvated
pH=12
Intensity (a. u.)
Intensity (a. u.)
Ethanol
pH=10 pH=7 Immersed in CHCl3
DMF
pH=4
o
Acvated at 150 C
Acvated at 150 oC
Simulated
10
15
20
25
30
Degrees (2-theat) Fig. 2 PXRD patterns of the MMPF after immersion in different solvents
meet the requirements of applications. Thus, seldom were MOFs reported to be chemically resistant in basic or acid medium. Strikingly, MMPF also exhibited amazing chemical stability and powder XRD results have suggested that they remained stable not only in boiling water but also in basic aqueous solutions with pH values in the range of 7–12 (Fig. 3 and Fig. S2). In fact, although the solution
123
10
15
20
25
30
Degrees (2-theat) Fig. 3 Powder X-ray diffraction (XRD) profiles for experimental MMPF soaked in boiling water and aqueous solutions with pH values ranging from 4 to 12 for 24 h
was also clear as shown in the Fig. S2, the MMPF has already decomposed in acid solution and turned into the metalloporphyrinic monomers. Hence, there was no obvious peak in XRD pattern (pH 4). Therefore, MMPFs showed an unprecedented high robustness in 3D framework in basic condition.
Efficient Catalyst Based on MMPF
593
3.2 Catalytic Activity
cyclohexene
Under present reaction condition, a range of alkenes were selected to be oxidized in this catalytic system (Table 2, entry 1–7). For substrates with different sizes, cyclohexene with a smaller steric size triggered a higher conversion with respect to cyclooctene as substrate (Table 2, entry 1–2). This observation highlighted that MMPF offered channels with accessible catalytic sites for the substrates, which greatly facilitated their diffusion. It should be mentioned that, increasing the length of linear alkenes triggered lower epoxide yield (Table 2, entry 3–5). Additionally, the low electron density of conjugated alkenes usually reduced their nucleophilicity towards electrophilic oxygen of porphyrin-MnV = O. Therefore, the conversion of styrene and trans-stilbene was very low, almost 50 % selectivity of epoxide existed during the oxidation (Table 2, entry 6–7). The kinetic profiles for the selective oxidation of substrates were also represented in Fig. 4 to gain insight into the catalytic behaviour. In fact, cyclohexene as substrate gave rise to a faster reaction, relative to cyclooctene as substrate. In addition, evident from Fig. 4, it was shown that the conversion increased in the order of cyclohexene [ cyclooctene [ 1-hexene [ styrene [ trans-stilbene [ 1-octene [ 1-dodecene.
Conversion (%)
80
cyclooctene 1-hexene 1-octene
60
1-dodecene styrene trans-slbene
40
20
0 0
100
200
300
400
500
Time (min) Fig. 4 Kinetic traces of various substrates epoxidation catalyzed by MMPF
The excellent heterogeneous catalysts should not only have high catalytic activity and selectivity, but should also be structurally stable and thus be easily recovered for continuous usage. Compound MMPF can be simply recycled by filtration, which was subsequently reused in successive runs. As expected, MMPF exhibited high catalytic activity in which 93 % cyclooctene could be oxidized into the cyclooctene epoxide product with 99 % selectivity after
Table 2 Scope of MMPF-catalyzed epoxidation of alkenesa Catalyst
Conversion (%)b
Selectivity (%)c
1
MMPF
93
[99
2
MMPF
100
[99
3
MMPF
65
[99
4
MMPF
4
[99
5
MMPF
–
–
6
MMPF
40
54
7
MMPF
31
50
Entry
Substrate
a
Olefin (500 mM), PhIO (10 mM), catalyst (5 mM), acetonitrile (5.0 mL) sealed and bromobenzene 50 mg as internal standard in a Teflonlined screw cap vial were stirred at room temperature for 24 h
b
Conversion [%]
c
Selectivity [%] were determined by GC using an SE-54 column (50 °C for 1 min, then 10 °C min-1 up to 140 °C and 140 °C for 15 min) based on the oxidant
123
594
W. Zhang et al. Table 3 Selective oxidation of cyclohexene catalyzed by MMPFa
100
(%)
80 60 40
3
Selectivity (%)c [99
MMPF
100
2
MnCl2
–
–
Selecvy
3
FeCl2
38
10
4
Mn-TCPP
17
[99
5
Mn-TCPP ? FeCl2
40
12
6
Filtrate1d/Filtrate2e
4/52
0/99
7
Blank
4
0
4
Recycling
Conversion (%)b
1
0 2
Catalyst
Conversion
20 1
Entry
Fig. 5 Catalyst recycling in the epoxidation of cyclooctene with MMPF as catalyst by PhIO
a
24 h in the second run (shown in Fig. 5). After four cycles, the recycled MMPF still exhibited a very high conversion of 90 % and selectivity of [99 %, thus indicating that MMPF was indeed a heterogeneous catalyst for cyclooctene epoxidation at room temperature (Fig. 5). As expected, the initial reaction rate decreased upon reuse (Fig. 6). According to the above results, it has been supposed that the active catalytic sites should be the Mn-porphyrin moieties within the pores in MMPF. To confirm the relationship between the structure and catalytic activity, we compared the catalytic activities of MMPF with their molecular components of MnCl2, FeCl2 and Mn-TCPP, and their mechanically combined mixtures under identical reaction conditions. MnCl2 and FeCl2 showed very low catalytic activity with conversions of 0 and 38 %, respectively (Table 3, entry 2–3). Mn-TCPP and/or FeCl2 did show quite moderate catalytic activity that could transform 40 % of the cyclohexene into the cyclohexene epoxide but still were not as efficient as heterogeneous MMPF (100 % conversion).The low activity observed for homogeneous Mn-TCPP could be attributed to catalyst deactivation as a result of the oxo-bridged dimer formation (Table 3, entry 4). The supernatant from oxidation of cyclohexene after filtration at the beginning through a regular filter did not
b
Cyclohexene (500 mM), PhIO (10 mM), catalyst (5 mM), acetonitrile (5.0 mL) and bromobenzene 50 mg as internal standard sealed in a Teflon-lined screw cap vial were stirred at room temperature for 24 h Conversion [%]
c
Selectivity [%] were determined by GC using an SE-54 column (50 °C for 1 min, then 10 °C min-1 up to 140 °C and 140 °C for 15 min) based on the oxidant
d
MMPF catalyst was removed at 0 h and then reaction solution was analysed after 24 h
e
The filtration time was 4 h
afford any additional oxidation product, which was basically as inactive as the blank (Table 3, entry 6–7). Another filtration test in MMPF has also been performed at 4 h (Table 3, entry 6). Accordingly, the epoxidation was allowed to proceed for 4 h before being filtered to remove any solid precipitate. Then, the supernatant was analysed after 24 h. Finally, the catalytic performance of oxidation increased slightly. This filtration test confirmed a truly heterogeneous process. Overall, the MMPF displayed a prior performance to Mn-TPP in epoxidation of cyclohexene, thus highlighting the high efficiency of 3D network-based nanochannel-reactor in MMPF via its structural resistance to formation of catalytically inactive species.
4 Conclusion 45
Conversion
40 35
(%)
30 25 20 15 10 5 0 1h 2h 4h
1h 2h 4h
1h 2h 4h
Recycling
Fig. 6 The initial reaction rate of catalyst recycling
123
1h 2h 4h
In summary, we have explored a novel metalloporphyrinic metal–organic framework, which endows MMPF with a solvent-induced breathing behaviour and resistance to basic solution. It has been demonstrated that MMPF was a good candidate for activation of unsaturated bonds. Noteworthy, MMPF exhibited high catalytic activity in which cyclohexene could be almost fully oxidized into the epoxide product with 99 % selectivity. On the other hand, various other unsaturated olefins with different steric sizes were investigated to confirm the catalytically active sites being located into the nanochannel of MMPF. Therefore, this work provided a promising platform to design functional networks as catalysts in selective oxidation.
Efficient Catalyst Based on MMPF Acknowledgments Special thanks to Dr. Z.C. Zhang from Huaihai Institute of Technology, China for his help on analysis of crystal structure. This work was supported financially by the National ‘‘Twelfth Five-Year’’ Plan for Science & Technology (2012BAD32B03), the National Natural Science Foundation of China (20903048) and the Innovation Foundation in Jiangsu Province of China (BY2013015-10).
References 1. Shaik S, Cohen S, Wang Y, Chen H, Kumar D, Thiel W (2010) Chem Rev 110:949 2. Costas M (2011) Coord Chem Rev 255:2912 3. Ortiz de Montellano PR (2010) Chem Rev 110:932 4. Kajiwara T, Higuchi M, Yuasa A, Higashimura H, Kitagawa S (2013) Chem Commun 49:10459 5. Nepal B, Das S (2013) Angew Chem Int Ed 52:7224 6. O’Keeffe M, Yaghi OM (2012) Chem Rev 112:675 7. Xuan W, Zhu C, Liu Y, Cui Y (2012) Chem Soc Rev 41:1677 8. Wang Z, Yuan S, Mason A, Reprogle B, Liu D-J, Yu L (2012) Macromolecules 45:7413 9. Dhakshinamoorthy A, Alvaro M, Garcia H (2011) Catal Sci Technol 1:856 10. Feng D, Gu ZY, Li JR, Jiang HL, Wei Z, Zhou HC (2012) Angew Chem Int Ed 51:10307 11. Fateeva A, Chater PA, Ireland CP, Tahir AA, Khimyak YZ, Wiper PV, Darwent JR, Rosseinsky MJ (2012) Angew Chem Int Ed 51:7440 12. Meng L, Cheng Q, Kim C, Gao WY, Wojtas L, Chen YS, Zaworotko MJ, Zhang XP, Ma S (2012) Angew Chem Int Ed 51:10082 13. Zou C, Zhang T, Xie MH, Yan L, Kong GQ, Yang XL, Ma A, Wu CD (2013) Inorg Chem 52:3620 14. Yang XL, Xie MH, Zou C, He Y, Chen B, O’Keeffe M, Wu CD (2012) J Am Chem Soc 134:10638 15. Takaishi S, DeMarco EJ, Pellin MJ, Farha OK, Hupp JT (2013) Chem Sci 4:1509
595 16. Garibay SJ, Weston MH, Mondloch JE, Colon YJ, Farha OK, Hupp JT, Nguyen ST (2013) CrystEngComm 15:1515 17. Low JJ, Benin AI, Jakubczak P, Abrahamian JF, Faheem SA, Willis RR (2009) J Am Chem Soc 131:15834 18. Liu J, Zhang F, Zou X, Yu G, Zhao N, Fan S, Zhu G (2013) Chem Commun 49:7430 19. Jiang HL, Feng D, Wang K, Gu ZY, Wei Z, Chen YP, Zhou HC (2013) J Am Chem Soc 135:13934 20. Horcajada P, Chalati T, Serre C, Gillet B, Sebrie C, Baati T, Eubank JF, Heurtaux D, Clayette P, Kreuz C, Chang JS, Hwang YK, Marsaud V, Bories PN, Cynober L, Gil S, Ferey G, Couvreur P, Gref R (2010) Nat Mater 9:172 21. Fateeva A, Horcajada P, Devic T, Serre C, Marrot J, Greneche JM, Morcrette M, Tarascon JM, Maurin G, Ferey G (2010) Eur J Inorg Chem 2010:3789 22. Horike S, Sugimoto M, Kongpatpanich K, Hijikata Y, Inukai M, Umeyama D, Kitao S, Seto M, Kitagawa S (2013) J Mater Chem A 1:3675 23. Horcajada P, Salles F, Wuttke S, Devic T, Heurtaux D, Maurin G, Vimont A, Daturi M, David O, Magnier E, Stock N, Filinchuk Y, Popov D, Riekel C, Fe´rey G, Serre C (2011) J Am Chem Soc 133:17839 24. Chevreau H, Devic T, Salles F, Maurin G, Stock N, Serre C (2013) Angew Chem Int Ed 52:5056 25. Fateeva A, Devautour-Vinot S, Heymans N, Devic T, Grene`che J-M, Wuttke S, Miller S, Lago A, Serre C, De Weireld G, Maurin G, Vimont A, Fe´rey G (2011) Chem Mater 23:4641 26. Lindsey JS, Schreiman IC, Hsu HC, Kearney PC, Marguerettaz AM (1987) J Org Chem 52:827 27. Adler AD (1970) J Inorg Nucl Chem 32:2443 28. de Sousa AN, de Carvalho MEMD, Idemori YM (2001) J Mol Catal A Chem 169:1 29. Nakagaki S, Machado G, Halma M, Dossantosmarangon A, Defreitascastro K, Mattoso N, Wypych F (2006) J Catal 242:110 30. Da Silva VS, Teixeira LI, Do Nascimento E, Idemori YM, DeFreitas-Silva G (2014) Appl Catal A Gen 469:124 31. Horcajada P, Gref R, Baati T, Allan PK, Maurin G, Couvreur P, Fe´rey G, Morris RE, Serre C (2011) Chem Rev 112:1232
123
