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

Abstract

Photocatalytic valorization of lignin to aromatic monomers by cleaving the Cβ–O bond is a promising approach for the 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. Density functional theory calculations showed that Cr present on the CZIS surface can provide appropriate free energy for the target reaction intermediate, reducing the uphill ΔG for cleaving the Cβ–O ether bond reaction of the Cα radical (Cα •) intermediate to form acetophenone and phenol (from 2.15 to −0.81 eV), which facilitate the photocatalytic PP-ol conversion. In addition, controlling the competitive hydrogen evolution on the photocatalyst surface by adjusting the alkalinity of the reaction solvent is also a key factor to improve the photocatalytic performance.

Zinc Indium Sulfide‐Based Photocatalysts for Selective Organic Transformations

“…They explored the potential to promote the C β À O bond cracking of lignin model compounds by manipulating the solvent mixture and the reaction's alkalinity (Figure 11c). [135] Their work achieved nearly complete conversion of 2-phenoxy-1-phenylethanol (PPol), a model compound, with the selectivity for the desired products -phenol and acetophenone -reaching impressive levels of 96 % and 95 %, respectively. The key to this high efficiency and selectivity was the ability of the Wang's group has made a significant contribution to the field of lignin valorization by developing an oxidationhydrogenolysis tandem strategy to cleave the αÀ CÀ OH bond of βÀ O-4 lignin-derived alcohols.…”

“…Copyright 2017, American Chemical Society. (b-d) Reprinted with permission [135]. Copyright 2023, Elsevier.…”