Promotion of Photocatalytic Lignin Models C-O Bond Cleavage by Cr-Doped Zinc Indium Sulfide in Alkaline Solvent

Photocatalytic valorization of lignin to aromatic monomersby cleavingthe C-beta-O bond is a promising approach forthe utilization of biomass resources. Herein, we achieved nearly 100%conversion of the model compound 2-phenoxy-1-phenylethanol (PP-ol),and the selectivity of phenol and acetophenone reached 96 and 95%,respectively, using water and Cr-doped ZnIn2S4 (CZIS) as the hydrogen source and photocatalyst, respectively. Densityfunctional theory calculations showed that Cr present on the CZISsurface can provide appropriate free energy for the target reactionintermediate, reducing the uphill Delta G for cleavingthe C-beta-O ether bond reaction of the C-alpha radical (C-alpha (center dot)) intermediateto form acetophenone and phenol (from 2.15 to -0.81 eV), whichfacilitate the photocatalytic PP-ol conversion. In addition, controllingthe competitive hydrogen evolution on the photocatalyst surface byadjusting the alkalinity of the reaction solvent is also a key factorto improve the photocatalytic performance.