Phase Transformation, Exceptional Quenching Efficiency, and Discriminative Recognition of Nitroaromatic Analytes in Hydrophobic, Nonporous Zn(II) Coordination Frameworks

Five-fold interpenetrated
Zn­(II) frameworks (1 and 2) have been prepared,
and an irreversible phase transformation from 1 to 2 is found to occur through a dissolution–recrystallization
process. Compound 1 exhibits the highest quenching efficiency
(>96%) for nitrobenzene at 7 ppm among luminescent coordination
polymers. Selective discrimination of nitroaromatic molecules including o-nitrophenol (o-NP), p-nitrophenol (p-NP), 2,4-dinitrophenol (DNP), and
2,4,6-trinitrophenol (TNP) is realized in 1 and 2 as a result of the fact that the framework–analyte
interaction affords characteristic emission signals. This observation
is the first case of a nonporous coordination framework for such discriminative
detection. Notably, significant hydrophobicity is evident in the framework 1 because of its surface roughness, which accounts for the
enhanced quenching ability.