Continuous flow Hantzsch ester–enabled photocatalytic valorization of lignin β-O-4 and epoxy resin models

Herein, we disclose a continuous flow photocatalytic strategy for the valorization of oxidized lignin β -O-4 and epoxy resin model compounds. Using an iridium-based photocatalyst and Hantzsch esters as hydrogen donors, the method enables selective reductive C O bond cleavage within 20 min, affording acetophenones and phenols as high value-added aromatic products in up to 91% yield. The protocol is readily extended to an oxidized epoxy resin model, enabling the formation of methylated bisphenol A and demonstrating its applicability beyond lignin-derived substrates. Collectively, these results establish a robust and scalable photoflow platform for the selective transformation of biomass- and polymer-derived C O linkages. • Photoflow cleavage of lignin models achieved 91% yield in 20 min reaction time. • Iridium photocatalyst enables selective C O bond cleavage under blue LED light irradiation. • Continuous flow reduces reaction time from 5 h to 20 min efficiently. • Method successfully applied to an epoxy resin model with 87% isolated yield. • Gram-scale synthesis demonstrates robustness for biomass valorization routes.