Visible-light-driven selective cleavage of CC bonds in lignin model substrates using carbon nitride-supported ruthenium single-atom catalyst

The selective cleavage of the C C bonds in lignin is highly pursued to obtain aromatic monomers from renewable resources but remains challenging due to their high dissociation energies and steric hindrance between bulky aromatic groups. Herein, a mesoporous carbon nitride-supported ruthenium single-atom photocatalyst (Ru 1 /MCN) is reported for efficient oxidative C α -C β bonds scissoring towards lignin β -O-4 model compounds with high activity and selectivity under visible–light irradiation and room temperature. With this strategy, a nearly total conversion of > 99% and > 98% selectivity of C C bond cleavage can be achieved upon 2–phenoxy–1–phenylethanol. In-depth investigations verify that the C β -H extraction by photogenerated holes is the critical step of the transformation, which directly generates the C β radical intermediates and thus promotes the selective C α -C β bonds breaking by coupling with superoxide radicals induced by photogenerated electrons. This work explores the potential of single-atom catalysts for photocatalytic production of aromatics from renewable biomass feedstocks.