Decoupling Light Absorption From Photocatalytic Reactivity in TiO ₂ via Defect and Interfacial Engineering

Titanium dioxide (TiO 2 ) is widely used as an inorganic UV filter because its wide bandgap (∼3.2 eV) enables strong UVB blocking; however, this same electronic structure intrinsically limits spectral coverage and promotes photocatalytic generation of reactive oxygen species (ROS). Here, we present a dual‐engineered inorganic photoprotective material that simultaneously expands UV‐to‐high energy visible (HEV) light attenuation and suppresses photo‐induced ROS generation by integrating abundant nitrogen (N) doping with a metal‐phenolic network (MPN) coating. Ammonia‐assisted thermal treatment introduces abundant nitrogen‐related defect states into TiO 2 , extending sub‐bandgap absorption into the UVA and HEV regions and promoting carrier recombination rather than photocatalytic charge transfer. Subsequent MPN coating further broadens optical attenuation via ligand‐to‐metal charge transfer (LMCT) and scavenges residual ROS through catechol and galloyl moieties. Consequently, SiO 2 /N‐TiO 2 /MPN achieves broad‐spectrum optical attenuation (99% UVB, 94% UVA, and 79% HEV), yielding approximately twofold and threefold enhancements in SPF and UVAPF compared to pristine SiO 2 /TiO 2 . The cooperative defect‐engineered core and redox‐active shell sustain suppression of apparent hydroxyl radical generation for 6 h under simulated solar irradiation, while in vitro cell viability assays indicate reduced irradiation‐induced cytotoxicity under controlled conditions. This strategy establishes a core‐shell paradigm for photochemically suppressed, broad‐spectrum inorganic UV filters.