Related Experiment Video
Updated: Jul 8, 2026

Developing Photosensitizer-Cobaloxime Hybrids for Solar-Driven H2 Production in Aqueous Aerobic Conditions
Published on: October 5, 2019
Photocatalytic Anaerobic Conversion of m-Xylene to Xylenols With Co-Production of Hydrogen
Zhuizhui Su1, Yonghua Tang2, Huanmin Liu1
1School of Environment and Energy, Peking University Shenzhen Graduate School, Shenzhen, Guangdong, People's Republic of China.
Abstract:
Mild photocatalytic valorization of aromatic hydrocarbons is promising for phenolic synthesis, but reliance on oxidants (O2 or H2O2) often leads to the oxidation of alkyl groups rather than stable phenyl rings, thus producing aromatic aldehydes or ketones instead of targeted phenols. In this work, we employed a photocatalytic anaerobic reaction pathway for directly synthesizing the targeted high-value xylenol and H2 from m-xylene and water over a palladium single atom-loaded TiO2 with zinc modification (Pd1-TiO2(Zn)). In situ infrared spectroscopy and electron paramagnetic resonance, in combination with first-principles simulations, revealed that the photocatalytic anaerobic conversion of m-xylene proceeds via surface lattice oxygen-mediated hydroxylation. Lattice oxygen coordinated with Pd acts as a recyclable oxygen source for phenolic hydroxyl groups, regenerated by the rate-determining water oxidation. Isotope labeling confirms hydroxyl hydrogen originates from the benzene ring, not water; water only provides oxygen. The zinc modification could significantly reduce the reaction barrier of the water-oxidation step from 0.85 to 0.22 eV at the Pd-O site. Therefore, the phenolic production rate over Pd1-TiO2(Zn) reached 376.9 µmol g-1 h-1, accompanied by an exceptionally high phenolic selectivity of 98.5% and a hydrogen production rate of 380.6 µmol g-1 h-1, 2-fold higher than that of unmodified Pd1-TiO2.
Related Concept Videos
Reduction of Benzene to Cyclohexane: Catalytic Hydrogenation
Reduction of Alkenes: Asymmetric Catalytic Hydrogenation
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
Reduction of Alkenes: Catalytic Hydrogenation
Metals like palladium, platinum, and nickel are commonly used in their solid forms — fine powder on an inert surface. As these catalysts remain insoluble in the reaction mixture, they are referred to as heterogeneous catalysts.
The hydrogenation process takes place on the surface of...
Hydrolysis of Chlorobenzene to Phenol: Dow Process
Radical Autoxidation
