Synthesis of Sm- and Eu- MOFs from 2,5-Diaminoterephthalic Acid for Selective Cationic Dye Adsorption and Luminescent Sensing of Nitroaromatic Compounds

This work describes the rational synthesis and comprehensive characterization of two amino-functionalized lanthanide-based MOFs, [Ln(2,5-(NH 2 ) 2 -BDC) 1 . 5 (DMF)(H 2 O)] (Ln = Sm, Eu), assembled from 2,5-diaminoterephthalic acid as a multifunctional organic linker. Single-crystal X-ray diffraction shows that both MOFs crystallize in the triclinic P-1 space group, forming 3D pcu-type networks with dinuclear Ln 2 O 16 nodes. PXRD confirmed phase purity, while FT-IR and TGA analyses verified ligand deprotonation and thermal stability up to ∼200 °C. The Eu-MOF exhibits mesoporous characteristics with a BET surface area of 8.32 m 2 g –1 and a pore diameter of 7.69 nm, designed for selective interactions rather than bulk adsorption. It shows strong, charge-selective adsorption toward the cationic dye methylene blue ( q e = 439.3 mg g –1 ) with minimal uptake of methyl orange, due to favorable electrostatic and π–π interactions. The Eu-MOF also displays intense red emission from the 5 D 0 → 7 F 2 transition, efficiently quenched by o -nitroaniline and picric acid. High Stern–Volmer constants (∼4.04 × 10 4 L mol –1 for o-NA and ∼4.01 × 10 4 L mol –1 for PA) with low detection limits (0.34–0.36 ppm) demonstrate excellent sensing ability. These Sm/Eu-MOFs thus show potential for selective dye adsorption and nitroaromatic sensing, highlighting their applicability in environmental remediation and pollutant detection.