Solid‐State Luminescent Responsive Bilayer Architecture Based on 2D Lanthanide MOFs for Ratiometric NO₂ and SO₂ Monitoring

The development of responsive materials for monitoring atmospheric toxic emissions is a growing area of interest. Luminescent metal-organic framework (LMOF), particularly those based on lanthanides (LnMOFs), have emerged as promising candidates due to their sharp emission bands, long luminescence lifetimes, and structural versatility. Despite their potential, the integration of LnMOFs into robust solid-state sensing platforms remains limited. In this study, we report the synthesis of three isostructural LnMOFs -[Tb₂(AATA)₃(DMF)₄], [Eu₂(AATA)₃(DMF)₄], [Gd₂(AATA)₃(DMF)₄]- based on the antenna-type ligand 2,5-bis(acetylamido)terephthalic acid, which promotes strong lanthanide emission and stable 2D frameworks. The MOFs were successfully embedded into polydimethylsiloxane (PDMS) to produce composite films retaining their luminescent properties in the solid state. We further present a conceptual bilayer configuration with one film acting as a stable internal reference, and the other serving as the analyte-responsive layer. This bilayer design enables ratiometric luminescence detection, thereby enhancing the accuracy and reliability of the measurements. As a proof-of-concept, we demonstrate that the bilayer films exhibit measurable luminescence changes in presence of two major atmospheric pollutants, NO₂ and SO₂. This result sets a foundational approach for developing more accurate and self-referencing luminescent materials.