Two novel multifunctional Cd(II)-MOFs based on benzimidazole-terpyridine ligand for high selective fluorescence...

Two novel Cd(II) Metal-Organic Frameworks (MOFs), namely, {[Cd(bimphtpy)(m-bdc)(H₂O)]·(H₂O)₃}_n (Cd-MOF-1) and {[Cd(bimphtpy)(tdc)(H₂O)]·(H₂O)₃}_n (Cd-MOF-1), have been assembled from two unique dicarboxylate ligands (m-H₂bdc = meta-benzenedicarboxylic acid, H₂tdc = 2,5-thiophenedicarboxylic acid) and 4'-(4-(1H-benzimidazol-1-yl)phenyl)-3,2':6',3″-terpyridine (bimphtpy), featuring two dimensional (2D) frameworks. Cd-MOF-1 and Cd-MOF-2 are isostructural, exhibiting undulated 2D layers with 4-connected sql topology. Within this structure, 1D channels (void fraction: 21.6 % for Cd-MOF-1 and 20.6 % for Cd-MOF-2) arise from parallelogram windows formed by vertex-sharing [Cd₄] nodes. Both Cd-MOF-1 and Cd-MOF-2 are promising quintuple-functional fluorescent sensors of Fe³⁺, Cr₂O₇^2-, Sulfathiazole (STZ), Oxytetracycline (OTC) and Nitrofurantoin (NFT) with high selectivity and sensitivity through luminescence quenching effects. The limits of detection (LOD) of Cd-MOF-1 and Cd-MOF-2 are 4.11 × 10^-6 mol·L^-1 and 7.84 × 10^-6 mol·L^-1 for Fe³⁺, 2.12 × 10^-6 mol·L^-1 and 1.32 × 10^-6 mol·L^-1 for Cr₂O₇^2-, 9.17 × 10^-7 mol·L^-1 and 1.79 × 10^-7 mol·L^-1 for STZ, 3.73 × 10^-7 mol·L^-1 and 5.51 × 10^-7 mol·L^-1 for OTC and 1.92 × 10^-7 mol·L^-1 and 5.58 × 10^-7 mol·L^-1 for NFT, respectively. Investigations into the plausible pathways for fluorescence quenching phenomena have integrated PXRD, UV-vis, fluorescence lifetime studies, and theoretical calculations. Moreover, CO₂ adsorption capacities quantified as 15.1 cm³ g^-1 for Cd-MOF-1 and 7.99 cm³ g^-1 for Cd-MOF-2 at 273 K and 1 bar have been determined. The dual-functional frameworks serve as gas separation materials and multi-analyte sensing platforms, enabling synchronous detection of Fe³⁺, Cr₂O₇^2-, STZ, OTC and NFT via analyte-specific quenching pathways.