Visible-Light-Driven Efficient Cleavage of β-O-4 Linkage in a Lignin Model Compound: Phenethyl Phenyl Ether Photocatalyzed by Titanium Nitride Nanoparticles

摘要

Producing valuable aromatics from lignin through controlled depolymerization has attracted much attention recently, especially with beta-O-4 linkage as the key target, which accounts for the highest ratio of lignin models. Phenethyl phenyl ether (PPE) is an ideal model compound containing this beta-O-4 model. Commercially available titanium nitride nanoparticles were employed to cleave the C-O bond in PPE with high selectivity to equivalent styrene and phenol under very mild conditions (100 degrees C and normal pressure) with isopropanol as the green solvent through a visible-light-driven photocatalytic process. Direct photon energy input and a free radical mechanism were responsible for this reaction. In addition, the Ti-N-O structure in TiN samples was confirmed to be the active site for cleavage of the C-O bond in PPE in the light reaction. This novel procedure shows obvious advantages over traditional thermolysis, such as mild conditions and no byproducts at all. This work provides a new visible-light-driven photocatalytic process, which is of great potential for the production of valuable aromatic compounds from lignin.