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Near-IR squaraine dye-loaded gated periodic mesoporous organosilica for photo-oxidation of phenol in a continuous-flow device.

Borah P, Sreejith S, Anees P, Menon NV, Kang Y, Ajayaghosh A, Zhao Y - Sci Adv (2015)

Bottom Line: The dye-loaded and azobenzene-gated PMO (Sq-azo@PMO) exhibits excellent generation of reactive oxygen species upon excitation at 664 nm, which can be effectively used for the oxidation of phenol into benzoquinone in aqueous solution.Furthermore, Sq-azo@PMO as the catalyst was placed inside a custom-built, continuous-flow device to carry out the photo-oxidation of phenol to benzoquinone in the presence of 664-nm light.By using the device, about 23% production of benzoquinone with 100% selectivity was achieved.

View Article: PubMed Central - PubMed

Affiliation: Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, 637371 Singapore, Singapore.

ABSTRACT
Periodic mesoporous organosilica (PMO) has been widely used for the fabrication of a variety of catalytically active materials. We report the preparation of novel photo-responsive PMO with azobenzene-gated pores. Upon activation, the azobenzene gate undergoes trans-cis isomerization, which allows an unsymmetrical near-infrared squaraine dye (Sq) to enter into the pores. The gate closure by cis-trans isomerization of the azobenzene unit leads to the safe loading of the monomeric dye inside the pores. The dye-loaded and azobenzene-gated PMO (Sq-azo@PMO) exhibits excellent generation of reactive oxygen species upon excitation at 664 nm, which can be effectively used for the oxidation of phenol into benzoquinone in aqueous solution. Furthermore, Sq-azo@PMO as the catalyst was placed inside a custom-built, continuous-flow device to carry out the photo-oxidation of phenol to benzoquinone in the presence of 664-nm light. By using the device, about 23% production of benzoquinone with 100% selectivity was achieved. The current research presents a prototype of transforming heterogeneous catalysts toward practical use.

No MeSH data available.


Related in: MedlinePlus

Photophysical studies of Sq-azo@PMO.(A) UV/Vis absorption spectra of Sq in dichloromethane (DCM) (red curve), trans-azo@PMO in water (black curve), and Sq-azo@PMO in water (blue curve). (B) Emission spectra of Sq in DCM (red curve) and Sq-azo@PMO in water (blue curve).
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Figure 3: Photophysical studies of Sq-azo@PMO.(A) UV/Vis absorption spectra of Sq in dichloromethane (DCM) (red curve), trans-azo@PMO in water (black curve), and Sq-azo@PMO in water (blue curve). (B) Emission spectra of Sq in DCM (red curve) and Sq-azo@PMO in water (blue curve).

Mentions: We then synthesized an unsymmetrical Sq dye by coupling half-squaraine with dimethoxy styrylpyrrole under azeotropic refluxing conditions in benzene/butanol (fig. S3). The dye was purified by column chromatography over silica gel and characterized by 1H NMR, 13C NMR, and high-resolution mass spectrometry. Sq exhibits a characteristic absorption maximum at 667 nm (ε = 165,620 M−1 cm−1, Fig. 3A) and a corresponding emission maximum at 685 nm (Fig. 3B) in dichloromethane.


Near-IR squaraine dye-loaded gated periodic mesoporous organosilica for photo-oxidation of phenol in a continuous-flow device.

Borah P, Sreejith S, Anees P, Menon NV, Kang Y, Ajayaghosh A, Zhao Y - Sci Adv (2015)

Photophysical studies of Sq-azo@PMO.(A) UV/Vis absorption spectra of Sq in dichloromethane (DCM) (red curve), trans-azo@PMO in water (black curve), and Sq-azo@PMO in water (blue curve). (B) Emission spectra of Sq in DCM (red curve) and Sq-azo@PMO in water (blue curve).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4643787&req=5

Figure 3: Photophysical studies of Sq-azo@PMO.(A) UV/Vis absorption spectra of Sq in dichloromethane (DCM) (red curve), trans-azo@PMO in water (black curve), and Sq-azo@PMO in water (blue curve). (B) Emission spectra of Sq in DCM (red curve) and Sq-azo@PMO in water (blue curve).
Mentions: We then synthesized an unsymmetrical Sq dye by coupling half-squaraine with dimethoxy styrylpyrrole under azeotropic refluxing conditions in benzene/butanol (fig. S3). The dye was purified by column chromatography over silica gel and characterized by 1H NMR, 13C NMR, and high-resolution mass spectrometry. Sq exhibits a characteristic absorption maximum at 667 nm (ε = 165,620 M−1 cm−1, Fig. 3A) and a corresponding emission maximum at 685 nm (Fig. 3B) in dichloromethane.

Bottom Line: The dye-loaded and azobenzene-gated PMO (Sq-azo@PMO) exhibits excellent generation of reactive oxygen species upon excitation at 664 nm, which can be effectively used for the oxidation of phenol into benzoquinone in aqueous solution.Furthermore, Sq-azo@PMO as the catalyst was placed inside a custom-built, continuous-flow device to carry out the photo-oxidation of phenol to benzoquinone in the presence of 664-nm light.By using the device, about 23% production of benzoquinone with 100% selectivity was achieved.

View Article: PubMed Central - PubMed

Affiliation: Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, 637371 Singapore, Singapore.

ABSTRACT
Periodic mesoporous organosilica (PMO) has been widely used for the fabrication of a variety of catalytically active materials. We report the preparation of novel photo-responsive PMO with azobenzene-gated pores. Upon activation, the azobenzene gate undergoes trans-cis isomerization, which allows an unsymmetrical near-infrared squaraine dye (Sq) to enter into the pores. The gate closure by cis-trans isomerization of the azobenzene unit leads to the safe loading of the monomeric dye inside the pores. The dye-loaded and azobenzene-gated PMO (Sq-azo@PMO) exhibits excellent generation of reactive oxygen species upon excitation at 664 nm, which can be effectively used for the oxidation of phenol into benzoquinone in aqueous solution. Furthermore, Sq-azo@PMO as the catalyst was placed inside a custom-built, continuous-flow device to carry out the photo-oxidation of phenol to benzoquinone in the presence of 664-nm light. By using the device, about 23% production of benzoquinone with 100% selectivity was achieved. The current research presents a prototype of transforming heterogeneous catalysts toward practical use.

No MeSH data available.


Related in: MedlinePlus