Rapidly Responsive Photogenerated Radical Unit for Achieving High-Contrast Photochromic Ionic Hydrogen-Bonded Organic Framework

Photochromic materials with high contrast have attracted much attention due to their ease of use and high safety. In this study, we successfully constructed a novel photochromic ionic hydrogen-bonded organic framework (iHOF-50) via a supramolecular self-assembly strategy. The framework consists of organic acids and amide salts derived from naphthalimide (NDI), which are interconnected through electrostatic interactions. Under ultraviolet (UV) irradiation, iHOF-50 can rapidly transition from white to black in a short period of time and reach its maximum response rate within 6 s. The electrostatic interactions and local deprotonation of iHOF-50 establish a stable pathway for photoinduced electron transfer, significantly enhancing effective exciton transitions under ultraviolet light and further improving the application reliability of the photochromic system. Furthermore, by doping iHOF-50 into poly(vinyl alcohol) (PVA), we fabricated a composite film (1%-iHOF-50-PVA) that not only preserves the excellent photochromism of iHOF-50 but also exhibits strong red fluorescence emission at 610 nm. This work expands the potential of iHOF-50 in multioptical crossover applications and offers new perspectives for the intelligent information security and anticounterfeiting technologies.