Divergent Adsorption-Dependent Luminescence of Amino-Functionalized Lanthanide Metal–Organic Frameworks for Highly Sensitive NO₂ Sensors

A novel gas sensing mechanism exploiting lanthanide luminescence modulation upon NO₂ adsorption is demonstrated here. Two isostructural lanthanide-based metal–organic frameworks (MOFs) are used, including an amino group as the sensitive recognition center for NO₂ molecules. The transfer of energy from the organic ligands to Ln is strongly dependent on the presence of NO₂, resulting in an unprecedented photoluminescent sensing scheme. Thereby, NO₂ exposition triggers either a reversible enhancement or a decrease in the luminescence intensity, depending on the lanthanide ion (Eu or Tb). Our experimental studies combined with density functional theory and complete active space self-consistent field calculations provide an understanding of the nature and effects of NO₂ interactions within the MOFs and the signal transduction mechanism.