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Lignin C-C bond cleavage induced by consecutive two-photon excitation of a metal-free photocatalyst.

Pengju LiRong LiuZijian ZhaoFushuang NiuKe Hu
Published in: Chemical communications (Cambridge, England) (2023)
Photocatalytic lignin valorization has caught widespread attention; yet the reaction systems often employ noble metal complexes, hydrogen atom transfer (HAT) agents, and/or sacrificial electron donors/acceptors that do not comply with atom economy or environmental friendliness. Herein, we discovered that N -phenylphenothiazine (PTH) as a metal-free photocatalyst induced the cleavage of the lignin C α -C β bond under ambient conditions free of those additional agents with a high yield and selectivity toward benzoic acid. Transient spectroscopic investigations revealed that the energy-demanding C α -C β bond cleavage was induced by the potent oxidant, 2 PTH˙ + *, that was derived from consecutive two-photon excitation of PTH.
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