Photo‐Stimuli‐Responsive Dual‐Emitting Luminescence of a Spiropyran‐Encapsulating Metal–Organic Framework for Dynamic Information Encryption

Abstract The development of photo‐stimuli‐responsive luminescent materials is essential to address emerging demands in encryption security. Here, a novel photo‐stimuli‐responsive dual‐emitting luminescent material ZJU‐128⊃SP (SP = spiropyran) is reported, which is obtained by encapsulating spiropyran molecules into a cadmium‐based metal–organic framework (MOF), [Cd3(TCPP)2]·4DMF·4H2O (ZJU‐128, H4TCPP = 2,3,5,6‐tetrakis (4‐carboxyphenyl)pyrazine). This MOF/dye composite ZJU‐128⊃SP exhibits a blue emission from the ligand of ZJU‐128 at 447 nm and a red emission around 650 nm from spiropyran. Utilizing the photoisomerization of spiropyran from ring‐closed to ring‐open form under UV‐light irradiation, significant fluorescence resonance energy transfer (FRET) process between ZJU‐128 and spiropyran is achieved. As a result, the blue emission of ZJU‐128 is gradually decreased while the red emission of spiropyran increases. This dynamic fluorescent behavior can fully recover to the original state following exposure to visible light (>405 nm). By taking advantage of the time‐dependent fluorescence, dynamical anti‐counterfeiting patterns and multiplexed coding are successfully developed based on ZJU‐128⊃SP film. This work provides an inspiring point for the design of information encryption materials with higher security requirements.