Tandem Solid-Solution Phase Post-Synthetic Modification of Porous Molecular Crystals for In-Situ Generation of Fluorophores

Conventional synthetic methods of organic luminescent molecules often involve labor-intensive solution-phase organic synthesis, which violate the principles of atom-economic transformation. Post-synthetic modification (PSM) offers a promising alternative, allowing direct transformation from one fluorophore to another. Although PSM is commonly implemented in extended frameworks, its application in porous molecular crystals remains challenging. Herein, we focus on utilizing porous molecular crystals, specifically tetraphenylethylene-cored frameworks, as versatile platforms for tandem PSM reactions to customize organic fluorophores. The tailored skeleton design ensures both the formation of porous structures and the occurrence of tandem solid-solution phase reactions while maintaining the solid state of reactants and products in each step. The inherent non-covalent bonding nature of the frameworks facilitates processing and characterization, offering unparalleled advantages for porous networks. The accompanying solid-state fluorescence transition from green to blue and then to green (or yellow) enables real-time monitoring of tandem reactions and provides intuitive mechanistic insights. This phenomenon is exploited for the facile construction of a dynamic information encryption system using fluorescent quick response codes. Tandem solid-solution phase post-synthetic modifications were realized based on porous molecular crystals. The sequential reactions involve addition reaction with hydrazine hydrate and condensation reaction with alkyl aldehydes, resulting in the production of three molecular frameworks in a quantitative manner, accompanied by solid-state fluorescence transition from green to blue and then to green (or yellow). image