A Reusable Fluorescent Molecular Self-Assembly Cage for Simultaneous Detection and Recycling of Silver(I) Ion.

Although molecular self-assembled porous materials capable of ratiometric fluorescence probing and recycling of metal ions are both economically and environmentally attractive, very few current efforts have been devoted. Herein, we demonstrated a three-dimensional pure organic cage, namely 4-cage, which can serve as a fluorescent probe for simultaneous ratiometric detection and recycling of Ag ion. Taking advantage of the promising emission behavior of its rigidified tetraphenylethylene scaffolds and the chelating ability of its dynamically reversible imine moieties, on one hand, upon the addition of Ag , 4-cage undergoes coordination to form a stable but poorly soluble fluorescent complex, Ag @4-cage, accompanied by a fluorescence color change from bluish-green to yellowish-green. This allows us to differentiate Ag from other cations with high selectivity. On the other hand, upon the addition of Cl anion, Ag @4-cage can be effectively converted into free 4-cage due to the competitive coordination of Cl with Ag . Through this process, secondary usage of 4-cage and the recycling of Ag ion can be achieved.