Luminescent PVDF/Ln-MOF composite films for selective detection of Cr (III), Cr (VI), Fe (III) and Ag (I) in water

The development of efficient, sensitive, and selective sensors for water contaminants is of paramount importance due to the increasing environmental and health concerns associated with metal ion pollution. In this work, lanthanide-based metal–organic frameworks (Ln-MOFs) were incorporated into PVDF membrane films to create robust and easy to use luminescent sensing platforms. Eu (III) and mixed-metal Eu/Tb MOFs were embedded via dip-coating. Uniform films with sufficiently good luminescent properties making the materials suitable as luminescent sensors were prepared named PVDF@[Eu 2 (BDC) 3 (H 2 O) 4 ] and PVDF@[Eu 0.2 Tb 1.8 (BDC) 3 (H 2 O) 4 ]. The films continue to demonstrate selective detection of Cr (III), Cr (VI), Fe (III), and Ag (I) in aqueous media. PVDF@[Eu 2 (BDC) 3 (H 2 O) 4 ] exhibited superior sensitivity toward Cr (III) (Ksv = 2162 M −1 , LOD = 111 µM), while PVDF@[Eu 0.2 Tb 1.8 (BDC) 3 (H 2 O) 4 ] was more responsive to Cr (VI) (Ksv = 5253 M −1 , LOD = 48 µM). The dual selectivity of these films enables differentiation between oxidation states of chromium. Both materials showed comparable quenching constants for Fe (III) (4–5 × 10 3 M −1 ) and significant responses to Ag (I). Permanent loss of luminescence was observed in the case of Cr (III), Fe (III) and Ag (I) suggesting destructive process. The samples demonstrate the potential of polymer-Ln-MOF composites as versatile and fast luminescent sensors for environmental monitoring applications.