Organic Polymorphs Based on AIE-Active Molecules: Preparation, Characterization, and Application

Organic solid materials with aggregation-induced emission (AIE) characteristics have good research value and development prospects owing to their excellent optical properties. Polymorphism-dependent emission behaviors have received more attention, as they provide a fundamental understanding of the relationship between molecular arrangements (packing or conformation) and photophysical properties. In this Review, we focus on various methods for preparing polymorphs and their applications due to polymorphism-dependent emission properties. First, various synthesis methods of AIE-active organic polymorphs are introduced, including not only conventional cultivation methods but also crystal-to-crystal transformation and supramolecular cocrystal and surfactant-assisted self-assembly strategies. Next, numerous characterization methods are mentioned that could be used to distinguish polymorphs and further explore their polymorphism-dependent properties. Then, the development and application of photofunctional polymorphs based on AIE-active organic molecules in diverse related areas are summarized. Finally, perspectives and challenges for the further development of AIE-active organic crystalline materials are addressed.