Guest‐Dependent Stimuli‐Responsive Photoluminescence in 0D Antimony Chlorides for Anticounterfeiting and Encryption Applications

Abstract 0D lead‐free metal halides with stimuli‐responsive photoluminescence (PL) have attracted great attention as promising smart materials for advanced anticounterfeiting and information encryption. However, designing high‐performance stimuli‐responsive metal halides remains a challenge. Herein, a solvent guest tuning strategy to develop stimuli‐responsive 0D metal halides is proposed. Three novel highly yellow‐emissive host‐guest systems, TMA₂SbCl₅·X (TMA: (CH₃)₄N⁺, X = DMSO, DMF, and MeCN) are synthesized. Under heat stimuli, TMA₂SbCl₅·X (X = DMSO and DMF) exhibits PL on‐off switching, while TMA₂SbCl₅·MeCN shows PL color change from yellow to orange, due to structural phase transitions. Particularly, TMA₂SbCl₅·DMSO and TMA₂SbCl₅·MeCN demonstrate a fast response within 50 s at temperatures above 353 K. Detailed in situ XRD diffraction study unveils the role of guest solvent molecules in the regulation of structural phase transitions. For the first time, it is found that the host‐guest systems possess a guest‐dependent structural evolution that results in a different PL response to heat stimuli. In addition, moister can also trigger structural phase transition and induce PL on‐off switching. The remarkable stimuli response performance makes these hybrids promising for anticounterfeiting and encryption applications. These findings provide new insights for the development of stimuli‐responsive lead‐free metal halide materials.