Photo‐Responsive Room‐Temperature Phosphorescent Films Exhibiting Photochromism and Time‐Dependent Phosphorescent Colors for Multilevel Anti‐Counterfeiting

ABSTRACT Developing dynamic color‐tunable room‐temperature phosphorescence (RTP) materials with photochromism and time‐dependent phosphorescence color (TDPC) presents a promising but highly challenging approach for achieving multilevel anti‐counterfeiting applications. Herein, we demonstrate a facile in situ synthesis strategy to photo‐responsive color‐tunable RTP polymer films with reversible photochromic and TDPC properties, which was achieved through rational integration of carboxyl‐functionalized spiropyran (SPCOOH) and luminescent hydrogen‐bonded organic framework formed by melamine (ME) and isophthalic acid (IPA) within the PVA amorphous matrix, mediated by synergistic hydrogen‐bonding networks. Crucially, UV‐induced spiropyran‐to‐merocyanine (SP→MC) isomerization enables a novel triplet‐singlet Förster resonance energy transfer (TS‐FRET) pathway between the ME‐IPA donor and MC acceptor, achieving precise modulation in afterglow color from cyan to orange. Moreover, the energy transfer creates distinct decay kinetics, thereby endowing the material with TDPC property. Furthermore, their multilevel time‐resolved multicolor dynamic anti‐counterfeiting applications have been demonstrated. This work establishes a simple and effective strategy for constructing TDPC systems to develop color‐tunable RTP materials.