Efficient and Selective C─C Bond Cleavage of Lignin into Aromatic Derivatives on Cs ₃ Sb ₂ Br ₉ Nanocrystal Photocatalysts

Abstract Lignin, derived from the abundant and renewable lignocellulosic biomass resource, stands as the predominant aromatic polymer. The pursuit of highly efficient catalysts for lignin depolymerization to yield valuable aromatic monomers with exceptional selectivity and high yields remains an ambitious yet formidable objective. Herein, the use of Cs 3 Sb 2 Br 9 nanocrystals (NCs) is reported as a photocatalyst for highly active and selective C−C bond cleavage of lignin to produce value‐added aromatic compounds. Surprisingly, a remarkable 2‐phenoxy‐1‐phenylethanol (PP‐ol) conversion rate of 100% and an impressive C−C cleavage selectivity of 97.5% to produce benzoic acid (yield of 93.7%) and phenyl format (yield of 97.4%) are achieved in the absence of any cocatalyst. Detailed experimental and theoretical analysis disclose that the selective activation and dehydrogenation process of C β ─H induced by the synergetic action of Sb Lewis acid sites and Br sites on the surface of Cs 3 Sb 2 Br 9 NCs significantly lowers the energy barrier for C−C bond cleavage, leading to highly active and selective lignin depolymerization. This study is expected to provide deep insights into boosting efficient lignin depolymerization via modulating the surface active sites of the catalyst, and may shed light on other solar energy conversion areas related to halide perovskites.