Stimuli-responsive smart materials exhibiting rapid and reversible color switching are highly desirable for emerging technologies. In this study, we present a covalent organic framework (PT-COF) constructed from tartaric acid dihydrazide (TAD) and an aldehyde monomer. During the synthesis process, partial in situ decomposition of TAD into hydrazine leads to a distinctive architecture incorporating both hydrazine linkages and residual TAD moieties. This dual-hydrophilic-site design enhances the framework's sensitivity to low-humidity, enabling ultrafast (<1.0 s) and fully reversible moisture-triggered naked-eye color switching of PT-COF between yellow and orange states, accompanied by reversible fluorescence intensity changes, with excellent cycling stability. The material demonstrates promising applications in advanced anticounterfeiting systems and sensitive metabolite detection platforms.
Li et al. (Mon,) studied this question.