Covalently Immobilized Lignin–Xanthene Conjugates for Persistent Surface Photochemistry and Self‐Sterilizing Interfaces Under Ambient Visible Light

Surface‐localized photochemical systems that operate under ambient visible light provide an attractive strategy for persistent self‐sterilizing interfaces. Here, we report a bio‐derived photoactive material platform based on covalently immobilized lignin–Eosin Y conjugates that enable stable, non‐leaching generation of reactive oxygen species (ROS) under low‐intensity visible light. Lignin was conjugated with the xanthene dye Eosin Y via benzophenone‐3,3′,4,4′‐tetracarboxylic dianhydride (BTDA) and further functionalized with methacrylate groups to produce a photoactive macromer (LBDRB). Incorporation of LBDRB into a UV‐curable acrylate formulation enabled rapid spray coating and photopolymerization, yielding mechanically robust films on diverse substrates. The resulting surfaces exhibited persistent photoactivity under both indoor lighting and sunlight, achieving efficient inactivation of Gram‐negative and Gram‐positive bacteria as well as enveloped RNA viruses. Notably, antibacterial activity was maintained for over one month and antiviral activity for up to two months, demonstrating long‐term photochemical durability. These results establish lignin–dye macromolecular networks as a scalable, bio‐derived platform for ambient‐light‐driven self‐sterilizing surfaces.