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

Abstract

Detecting NO2 in an efficient manner is probably one of the major challenges to ensure a desired level of air quality. In spite of great efforts to surpass the current limitations, the commercial techniques are still strongly affected by interferences, are costly or difficult to implement in the field. Here, we investigate lanthanide metal-organic frameworks (Ln-MOF) for NO2 sensing with the aim of proposing a novel approach to surpass the present limitations. Precisely, two isostructural luminescent Ln-MOFs have been used including a recognition center (amino-group) that provides high selectivity for NO2 molecules. Energy transfer from the organic ligands to Ln is strongly dependent on the presence of NO2, resulting in an unprecedented photo-luminescent sensing scheme. Thereby, NO2 exposition triggers either a reversible enhancement or a decrease of the luminescence intensity, depending on the lanthanide (Eu or Tb). Our experimental studies combined with DFT and complete active space self-consistent field calculations, provide understanding of the nature and effects of NO2 interactions within the MOFs and the signal transduction mechanism.

A Fluorescent Metal–Organic Framework for Food Real‐Time Visual Monitoring

“…It is known that H 2 atpt is an ideal “antenna chromophore” to sensitize Eu 3+ . [ 23 ] As displayed in Figure 1e, the EuMOF aqueous solution revealed the characteristic narrow‐band emission peaks at 578 ( 5 D 0 → 7 F 0 ), 590 ( 5 D 0 → 7 F 1 ), 611 ( 5 D 0 → 7 F 2 ), 646 ( 5 D 0 → 7 F 3 ), and 696 nm ( 5 D 0 → 7 F 4 ). [ 24 ] When the FITC was coupled to the EuMOF, the resultant EuMOF‐FITC was also well‐dispersed in water and showed characteristic Eu 3+ and FITC luminescence with well‐resolved emission bands.…”

Metal-Organic-Frameworks: Low Temperature Gas Sensing and Air Quality Monitoring

“…Luminescent MOFs (LMOFs) are widely used in gas sensing because of their excellent optical response towards guest molecules inside their cavities. Gas sensors, fabricated using two lanthanide-based MOFs (Tb-MOF and Eu-MOF, formed by 2-amino-1,4-benzene dicarboxylic acid with europium and terbium salts, respectively), were reported by Gamonal et al [84] for NO 2 gas detection with an LOD of 2.2 ppm at room temperature. The sensing mechanism was based on the rise in Eu 3+ luminosity and the reduction in Tb 3+ luminescence upon exposure to NO 2 gas.…”

A luminescent Tb3+ cholate hydrogel-based multi-functionalized platform for Hg2+ and NO2 detection

“…45 Therefore, systems based on the luminescence of lanthanides are superior, to some extent. In fact, due to the self-restriction of the parity f-f transitions, the luminescence of lanthanides is weak, and intriguingly, there are only a few reports on the determination of Hg 2+ in water [46][47][48][49] or NO 2 in the air [40][41][42]50 by lanthanide luminescence. It seems that the key point to solving the problem should be to find suitable organic ligands, especially aromatic compounds, which will sensitize and produce strong luminescence (the ''antenna effect''); i.e., the excited ligand molecules will nonradiatively transfer the energy to the 7 F 5 states such as Tb 3+ ions.…”