Photocatalytic transfer hydrogenolysis of aryl ethers

Aryl ethers greatly influence lignin depolymerization and the oxygen content in lignin products. Cleaving aryl ethers normally requires harsh conditions such as high-pressure hydrogen gas and elevated temperature. Herein, we developed a synergistic method that combines photocatalytic hydrogen transfer with acid catalysis for H-2-free hydrogenolysis of diphenyl ether and aromatic oxygenates at room temperature. The electron-enriched Pt/TiO2 surface stored abundant hydrogen species under light irradiation and efficiently catalyzed hydrogen transfer from isopropanol to aryl ethers. The acid mediated the hydrogenation sequence into: hydrogenolysis of aryl C-O bonds > saturation of aryl rings >> hydrogenolysis of aliphatic C-O bonds. DFT calculations suggested the aryl ether bond adsorbed on the Pt surface was weakened through protonation. This method delivered 98% yield of aliphatic monomers (73% cyclohexane and 25% cyclohexanol) from cleavage of diphenyl ether, and converted aromatic mixtures into cycloalkanes (57%) and aliphatic alcohols (9%) under mild conditions.

Automated summary

We developed a synergistic method combining photocatalytic hydrogen transfer with acid catalysis for H2-free hydrogenolysis of diphenyl ether and aromatic oxygenates at room temperature. The method achieved efficient conversion of diphenyl ether to aliphatic monomers (98% yield) and aromatic mixtures to cycloalkanes (57%) and aliphatic alcohols (9%) under mild conditions.