Ultra-high Surface Area Functional Porous Polymers
COMMUNICATION
flask was left stirring in the ice bath for a further 45 min to ensure uni-
form dispersion of FeCl3. The sealed flask was then placed in an oil bath
at 808C and heated for a period of 18 h. The reaction was then quenched
by the addition of methanol (40 mL) then filtered under gravity. It was
then washed with methanol (3ꢃ20 mL) and 0.1m HNO3 (aq) (3ꢃ20 mL)
then in soxhlet apparatus with acetone for 24 h. The product was then
dried at 508C in vacuo for 24 h. A similar procedure was used for poly-
mer beads.
mance: the most efficient catalytic performance is obtained
with HXL-PHP-MAP in diethyl ether, possibly due to the
higher polarity of this solvent and, therefore, its better suita-
bility for nucleophilic reactions. HXL-PHP-MAP out-per-
forms HXL-B-MAP, as is shown in Figure 3B. After three
hours, conversion of methylcyclohexanol is only 68%, com-
pared to 100% with HXL-PHP-MAP. This indicates the
more rapid mass transfer to the surface enabled by the
much more open pore morphology of polyHIPE, which per-
mits convective flow within this material. Un-hypercros-
slinked beads (B-MAP) similarly are outperformed by
HXL-B-MAP due to low swellability of the former in dieth-
yl ether. The performance of these beads in toluene is simi-
lar to that reported previously for the same polymer sup-
ported catalyst and catalytic reaction (data not shown), al-
though the catalyst loadings are different.[8a] The ability of
these beads to give any conversion of methylcyclohexanol in
diethyl ether is presumably due to the presence of signifi-
cant quantities of MAP on the surface of the beads (the
overall loading is quite high, see Table 1). To investigate cat-
alyst recyclability, a sample of HXL-PHP-MAP was used
five times without significant loss of activity (Figure 3C).
This confirms the covalent attachment and minimal leakage
of the catalyst, as well as the possibility of reusing the sup-
ported catalyst.
Functionalisation of HXL-PHP with 4-(methylamino)pyridine: A dry,
250 mL 3-necked flask equipped with a reflux condenser and magnetic
stirrer bar was purged with nitrogen, then dry NaH (0.68 g, 28.5 mmol),
and dry THF (10 mL) were added. 4-(Methylamino)pyridine (1.10 g,
10.2 mmol) dissolved in dry THF (20 mL) was injected into the flask and
the resulting solution was heated to reflux in an oil bath for 1 h. After
this time, HXL-PHP (0.55 g, 2.03 mmol of reactive groups) was added
quickly through the central neck, maintaining a blanket of nitrogen. The
flask was then heated to 508C for a period of 30 min. The reaction was
quenched and the product precipitated by pouring the reaction mixture
into an excess of methanol. The polymer was filtered and washed with
THF/H2O (3ꢃ20 mL), THF/0.1m HNO3 (aq) (3ꢃ20 mL), THF/H2O (3ꢃ
20 mL) and methanol (3ꢃ20 mL). The washed product was then dried in
vacuo for 24 h. A similar procedure was used for other polymers.
Catalytic testing: 1-Methylcyclohexanol (1.0 mL, 8.1 mmol), toluene
(7 mL) or diethyl ether and the catalyst (1 mol%) were added to a flask
and stirred under nitrogen for 15 min. After this time, acetic anhydride
(1.5 mL, 15.8 mmol) was injected into the flask. The reaction mixture was
allowed to react at room temperature for a given period of time, after
which the polymer was filtered, washed with solvent (toluene or diethyl
ether) and transferred to a sealed vial and submitted for analysis by gas
chromatography.
In conclusion, we have demonstrated the ability to control
the extent of hypercrosslinking of pVBC polyHIPE materi-
als to derivatise the surface with molecules of interest. This
has been demonstrated by attaching 4-(N-methylamino)pyri-
dine (MAP) to give a polyHIPE-supported version of the
nucleophilic catalyst DMAP. The MAP immobilised on hy-
percrosslinked polyHIPE is shown to be highly efficient in
the acylation of a tertiary alcohol and significantly outper-
forms both un-hypercrosslinked polyHIPE and hypercros-
slinked beads. The materials in monolithic form could be in-
stalled in columns to conduct such catalytic transformations
under flow.
Acknowledgements
This work was supported by an International Joint Project grant from the
Royal Society [JP062046].
Keywords: acylation
·
microporous
polymers
·
organocatalysts · porosity · supported catalysts
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[4] a) K. Y. Lee, J. H. Gong, J. N. Kim, Bull. Korean Chem. Soc. 2002,
23, 659–660; b) R. Octavio, M. A. de Souza, M. L. A. A. Vasconcel-
[5] a) C. Bonduelle, B. Martin-Vaca, F. P. Cossio, D. Bourissou, Chem.
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Experimental Section
Preparation of 4-vinylbenzyl chloride/divinylbenzene polyHIPE material:
100 mL of an aqueous phase, consisting of K2S2O8 (0.11 g, 0.41 mmol) in
deionised water (100 mL), was added dropwise with continuous stirring
at 300 rpm to an oil phase, consisting of 4-vinylbenzyl chloride (11.62 g,
76 mmol), divinylbenzene (0.25 g, 1.9 mmol), and the surfactant sorbitan
monooleate (Span 80; 2.20 g). The emulsion was stirred for another
30 min after addition of the aqueous phase, then transferred to a mold
for curing (24 h at 608C). The resulting polyHIPE was purified by Soxh-
let extraction (deionised water and acetone, both for 24 h) then dried in
vacuo for 24 h.
Hypercrosslinking of polyHIPE: Powdered polyHIPE (1 g, 3.67 mmol
chlorine per gram) was placed in a flask, 1,2-dichloroethane (80 mL) was
added and the neck was fitted with a rubber septum. The mixture was de-
gassed under a stream of nitrogen for 15 min with constant stirring, after
which time the nitrogen supply was removed and the sealed flask left for
a further 45 min (with stirring) to swell the polymer. The flask was then
placed in an ice bath and FeCl3 (1.09 g, 6.7 mmol) was added quickly
through the neck of the flask. The flask was then resealed and degassed
again for a period of 15 min. After removal of the nitrogen supply, the
Chem. Eur. J. 2010, 16, 2350 – 2354
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