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

•A nearly total conversion and > 98% selectivity of C-C bond cleavage is achieved.•Sufficient superoxide radicals are necessary for highly selective C-C bond cleavage under visible light.•Efficient photocatalytic C-C bonds breaking towards lignin β-O-4 model compounds.•Ru single atoms outperform the nanoparticles for photocatalytic C-C bond cleavage.•Cβ-H extraction by photogenerated hole is the critical step of the transformation.