High Fluorescence Porous Organic Cage for Sensing Divalent Palladium Ion and Encapsulating Fine Palladium Nanoparticles

Comprehensive Summary Porous organic cages (POCs) as an innovative type of porous molecular materials enable multifunctional applications. Herein, a fluorescence POC (denoted as 1) has been constructed by means of 5,5'-((2,5-dimethoxy-1,4-phenylene)bis(ethyne-2,1-diyl))diisophthalaldehyde condensing with cyclohexanediamine enantiomer with the aid of trifluoroacetic acid. 1 exhibits the permanent void and prominent fluorescence with relative quantum yield of 73% confirmed by gas sorption and emission experiments, respectively. Moreover, this organic cage is capable of sensing diavalent Pd2+ according to the fluorescence response to the addition of various metal ions. The dispersion of 1 in methanol containing palladium acetate was stirred at 25 C-o and then 80 C-o to reduce Pd2+ ions into nanoparticles (NPs), leading to the composite (Pd@1) composed of fine Pd NPs with the size of ca. 1.8 nm. The catalytic nature of Pd@1 over NaBH4 promoted the degeneration of nitrobenzene and congo red. This work introduces one new case of POCs with versatile properties and functions, including ion fluorescence recognition, fine Pd NPs stabilizer, and gas adsorption, enriching the family of POC-based materials.