Visible-Light-Driven Efficient Cleavage of β-O-4 Linkage in a Lignin Model Compound: Phenethyl Phenyl Ether Photocatalyzed by Titanium Nitride Nanoparticles
Zhe Liu, Yiming Huang, Gang Xiao, Peifeng Li, Haijia Su, Sarina Sarina, Huaiyong Zhu
Abstract
Producing valuable aromatics from lignin through controlled depolymerization has attracted much attention recently, especially with β-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 β-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 °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.