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TiO2 Nanoparticles Enabling Photocatalytic Desulfurization for C-C Coupling Reaction Using Visible Light
Shea Stewart1, Matas Simukaitis1, H Christopher Fry2
1Department of Chemistry, Temple University, 1901 North 13th Street, Philadelphia, Pennsylvania 19122, United States.
This study reveals a new visible-light photocatalysis mechanism using titanium dioxide (TiO2) nanoparticles. A surface thiol-Ti complex absorbs visible light, enabling efficient thiol desulfurization and C-S bond cleavage.
Area of Science:
- Photocatalysis
- Materials Science
- Organic Chemistry
Background:
- Titanium dioxide (TiO2) is a UV-active photocatalyst.
- Visible-light photocatalysis is desirable for sustainable chemical reactions.
- Thiol desulfurization is an important chemical transformation.
Purpose of the Study:
- To elucidate the mechanism of visible-light-driven photocatalytic desulfurization of thiols on TiO2 nanoparticles.
- To identify the role of surface complexes in visible-light absorption and activation.
- To provide a framework for extending visible-light reactivity to wide-bandgap metal oxides.
Main Methods:
- Diffuse reflectance infrared spectroscopy
- Cryogenic electron paramagnetic resonance spectroscopy
- LED illumination (>420 nm)
Main Results:
- Formation of a surface thiol-Ti charge-transfer complex was verified.
- This complex introduces visible-light absorption to the TiO2 system.
- Selective photoexcitation of the complex drives C-S bond scission without band gap excitation.
- Carbon-centered radicals were formed and coupled with styrene.
Conclusions:
- A surface-mediated mechanism for visible-light photocatalysis was uncovered.
- Charge-transfer complex formation dictates light absorption and chemical activation.
- This mechanism offers a pathway for visible-light utilization in TiO2 photocatalysis.
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