Two unusual nanocage-based Ln-MOFs with triazole sites: highly fluorescent sensing for Fe³⁺ and Cr₂O₇ ²⁻, and selective CO₂ capture

Luminescent metal–organic frameworks (LMOFs) containing fluorescent probes for the detection of pollutants such as organic solvents and heavy metals are becoming increasingly important, with lanthanide-MOF (Ln-MOF) materials receiving greater attention owing to the possibility of achieving fine-tuned luminescent properties. Herein, two unusual isostructural nanocage-based three-dimensional Ln-MOFs, 1-Ln (Ln=Tb, Eu), are constructed, using a new diisophthalate ligand with active Lewis basic triazole sites. Selective gas adsorption, especially the removal of CO₂ from CH₄, a primary component of natural gas and biogas, is desirable in terms of both economic and environmental considerations. 1-Eu is found to exhibit highly efficient luminescent sensing for Fe³⁺ cations and Cr₂O₇ ²⁻ anions, as well as selective CO₂ capture over CH₄.