Highly Water-Stable Novel Lanthanide Wheel Cluster Organic Frameworks Featuring Coexistence of Hydrophilic Cagelike Chambers and Hydrophobic Nanosized Channels

In attempts to investigate
the potential luminescent sensing materials for sensitive detection
of environmental pollutants, a new family of lanthanide wheel cluster
organic frameworks (Ln-WCOFs) UJN-Ln4 has been constructed
by employing one of the cycloalkane dicarboxylic acid derivatives.
Adopting different conformations, the ligand links Ln4 second
building units (SBUs) and Ln24 tertiary building units
(TBUs) to form a unique wheel cluster layer-pillared 3D framework
featuring the coexistence of hydrophobic nanosized channels and trigonal
antiprism arrays with hydrophilic cagelike chambers. Apart from charming
structures, isostructural UJN-Ln4 displays interesting
porous, water-stable features. Systematic luminescence studies demonstrate
that solvent water molecules can enhance the emission intensity of
solid-state UJN-Eu4. Acting as a recyclable luminescent
probe, water-stable luminescent UJN-Eu4 exhibits superior
“turn-off” detection for Fe3+ and Cu2+ ions in aqueous solutions. Due to the nanosized hydrophobic
channels, UJN-Eu4 also shows highly sensitive sensing
of sodium dodecyl benzenesulfonate (SDBS) via luminescence “turn-on”
respondence, representing the first example of quantitatively detecting
SDBS in aqueous solutions by employing luminescent lanthanide frameworks
as fluorescent sensors. The results also open up the exploration of
novel luminescent Ln-WCOFs exhibiting unique applications in sensitive
detecting of harmful pollutants in aquatic environments.