Advanced Time‐Resolved Information Security Protection From Synergistic Effect of FRET and Reversible Photoresponsive iHOF

Abstract Developing multi‐dimensional advanced encryption and anti‐counterfeiting technologies is an effective way to address the growing global problem of information security. Due to the rapid radical photochromism and great optical properties, 1,4,5,8‐naphthalenediimides (NDIs) have been widely applied in the field of information encryption. Herein, an ionic hydrogen‐bonded organic framework ( iHOF‐35 ) self‐assembled from chiral organic acid with photochromic groups NDI and organic base amidinium is reported. Under 365 nm illumination, NDI photogenerated radicals enable iHOF‐35 to exhibit rapid, reversible, and high‐contrast stimulus response behaviors in both solid and solution states. The applications in binary codes, QR codes, multicolor fluorescent cryptographic inks, and orthogonal encryption combining 2D and 3D codes have also been explored. In addition, 1%‐iHOF‐35‐PVA flexible anti‐counterfeiting composite membrane has been developed by doping iHOF‐35 with polyvinyl alcohol (PVA). 1%‐iHOF‐35‐PVA exhibits a fast synergistic response of NDI radical and the Förster resonance energy transfer (FRET), displaying various information on a time scale, and only showing valid information at a specific time. An in‐depth exploration of this time‐varying information encryption material in 4D information coding, as well as dynamic fluorescent images. This multi‐dimensional, multi‐form advanced encryption and anti‐counterfeiting technology is considered to be a favorable candidate material in the field of encryption.