Y. Tan et al. / Inorganic Chemistry Communications 14 (2011) 1966–1970
1969
ethanol. The reaction mixture was then stirred vigorously at 333 K for
h. At the end of the reaction, the catalyst was removed by filtration.
2
Ethanol was taken away by vacuum distillation. The amount of conden-
sation product was determined using a gas chromatograph GC/MS
Trance DSQ system (gas chromatograph coupled to a mass spectrome-
ter; carrier gas—nitrogen; flow, 1 ml/min; oven, 80–280 °C; injector,
8
9
0 °C; detector, 280 °C). It is interesting to observe that 37% and
9% conversions are obtained for the condensation adducts ethyl
(
E)-α-cyanocinnamate and 2-benzylidenemalononitrile respective-
ly (Fig. 2). The size of the reactive molecules is the reason for the
different yields. Catalysis efficiency depends on the interactions be-
tween the reactant and the catalyst. The smaller molecule is easily
to be accommodated into the channels and activated by the nitrogen
base sites. These results support that compound 1 is an efficient base
catalyst with a size selective property.
The stability of compound 1 is characterized by the X-ray powder
diffraction (XRPD) data (Fig. 3) and thermo gravity analysis (TG) data
(
Fig. 4). Phase purity of the bulk sample is confirmed by comparison
of the simulated and observed XRPD patterns. The same XRPD pat-
terns indicate that the catalyst remains its crystalline and framework
stability before and after the catalysis process. The TG data show that
compound 1 begins to be decomposed at 420 °C. The stable catalyst is
easily to be regenerated for the next cycle.
In conclusion, nitrogen containing ligands tpt and 2-atp are select-
ed to construct the functional channel with base catalytic sites. The
connections between the zinc centers and the mixed-ligands generate
a new MOF based heterogeneous catalyst. The test of the Knoevenagel
condensation was carried out with compound 1 as base catalyst. The
experiment data show that it is a stable and efficient base catalyst
with an interesting size selectivity character. It can be anticipated that
more MOF based catalysts may be designed and prepared for basic het-
erogeneous catalytic process via crystal engineering approach.
Fig. 3. PXRD patterns for compound 1: (a) simulated; (b) sample before catalytic pro-
cess; (c) sample after catalytic process of benzaldehyde with ethyl cyanoacetate; and
(d) sample after catalytic process of benzaldehyde with malononitrile.
channel, providing the active base sites for the catalysis reaction. The
iodide ion protrudes out from the layer acting as a terminal ligand. No
guest molecule is included in the pores. This character prevents the
structural collapse after the removal of small guest molecules. The
stacks of layers along the b axis are interlocked to give a 3D supramolec-
ular structural motif via π–π interactions (Fig. 1c). The π ring planes
overlap in a parallel-displaced mode [25]. These weak interactions
contribute to the stability of the framework of the structures.
Appendix A. Supplementary materials
Supplementary data to this article can be found online at doi:10.
1
016/j.inoche.2011.09.022.
References
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trile) is carried out to test the base catalytic ability of compound 1
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Fig. 4. The TGA diagram for compound 1.