Ti-MOF-derived titanium oxide-modified carbon nitride: A Z-scheme heterostructure for the selective photocatalytic cleavage of lignin CC bonds

The utilization of solar energy to break the C α C β bonds in lignin under mild conditions is highly important for lignin valorization. This work presents an MIL-125-derived titanium oxide (M-TiO 2 )-modified carbon nitride (g-C 3 N 4 ) heterostructure for selective photocatalytic lignin C α C β bond cleavage at room temperature. The conversion of lignin model 2-phenoxy-1-phenylethanol (PP-ol) reached 90.8 % over M-TiO 2 /g-C 3 N 4 composites, which is visibly higher than that of bare M-TiO 2 (33.2 %) and g-C 3 N 4 (57.3 %). Furthermore, the selectivity of C α C β bond breakage reached 96.8 %, and the yield of benzaldehyde was as high as 86.4 %. A mechanistic study innovatively demonstrated that lignin C α C β bond cleavages are achieved by the cooperative effect between holes and 1 O 2 , where holes dominate PP-ol conversion, whereas 1 O 2 governs C α C β bond cleavages. M-TiO 2 has relatively large surface areas and high porosities, and the Z-scheme heterojunctions retard charge carrier recombination and outfit strong redox abilities, which separately prompt O 2 adsorption and evolution to generate 1 O 2 , accounting for the high selectivity of C α C β bond breakages over M-TiO 2 /g-C 3 N 4 composites. This study sheds new light on the potential of metal–organic framework-derived materials in photocatalysis and provides valuable insights into the photocatalytic cleavage of lignin C α C β bonds.