Conjugated porous Polymers as Highly Efficient Heterogeneous Visible Light Photocatalyst
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hotopolymerization of MMA with B-(BOC-CB)2-BO Typical polymerization procedure: In a glass vial, a mixture of MMA (1 mL, 9,39 mmol), B-(BOC-CB)2-BO (25 mg) and Et3N (20 mg) were added. The mixture was purged with N2 for 5 min and the vial was sealed from air. The mixture was then irradiated with a 23 W household energy saving lamp (Osram) for 24 h. After the irradiation, the mixture was dissolved in more THF, the insoluble B-(BOC-CB2)-BO was filtered off and the product precipitated in methanol. PMMA was collected by filtration and dried under vacuum at 40 oC overnight. DISCUSSION Surface area and pore size distribution were measured via nitrogen sorption at 77.3 K based on the Brunauer-Emmett-Teller (BET) theory. The BET surface area for B-(Boc-CB)2-BT is 26 m2 g-1 whereas BET surface area for B-(Boc-CB)2BO is 82 m2 g-1. SEM images of the two porous polymers are displayed in Figure 1c and 1d, which show interconnected pore structures throughout the polymers. The cavities of the polymers range from 10 m to 20 m in size whereas the interconnected pores have diameters of about 1 m.
Figure 1. (a) Idealized structure of B-(BOC-CB2)-BO: X = O and B-(BOC-CB2)-BT: X = S (b) DRS UV/Vis spectra of B-(BOC-CB2)-BO and B-(BOC-CB2)-BT (c) SEM image of B-(BOCCB2)-BT (d) SEM image of B-(BOC-CB2)-BO The photocatalytic activity of B-(BOC-CB2)-BT as heterogeneous photocatalyst under visible light was investigated with the photooxidation of thioanisole at room temperature in acetonitrile. Conversion of the photocatalytic reaction was determined by integrating the 1H-
NMR spectra of the reaction mixtures assigned to thioanisole and the products i.e. methyl phenyl sulfoxide and methyl phenyl sulfone. As shown in Table 1, quantitative selectivity up to >99% of the photooxidation of thioanisole into the desired mono-oxidized product methyl phenyl sulfoxide was achieved. Table 1: Selective oxidation of various sulfides using B-(Boc-CB2)-BT as photocatalyst under visible light irradiation.* Selectivity (%) Time Conversion Entry (h) (%) 1
24
>99
95
5
2
24
98
>99
99
99
99
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