Design and Construction of a Porphyrin-Based Samarium(III)-Metal-Organic Framework for Antibiotic Detection

Porphyrins bearing the unique 18π electron tetrapyrrolic macrocycles exhibit interesting photophysical and photochemical properties and have been considered as promising ligands for the construction of functionalized metal-organic frameworks (MOFs). The combination of porphyrin-type ligands with lanthanide metals featured with diverse coordination environments to realize the novel functions as well as the diversity of the MOF is thus attractive but challenging. Herein, an unprecedented porphyrin-based samarium MOF (Sm-BCPP) composed of a 5,10-bis(4-carboxyphenyl)-10,20-diphenyl porphyrin (H₂BCPP) ligand and samarium-formed one-dimensional clusters has been constructed via a solvothermal approach, and the synthesized Sm-BCPP has excellent chemical stabilities, exhibiting red luminescence. Interestingly, Sm-BCPP demonstrated excellent fluorescence quenching against commonly used antibiotics, showing an ultrahigh fluorescence quenching constant (K_SV) and ultralow detection limit (LOD), among which the detection limit of rifampicin (LOD = 0.33 nM) and nitrofurazone (LOD = 0.24 nM) was found to be lower than most reported MOF materials. Encouragingly, the Sm-BCPP MOF exhibited excellent stability in aqueous solutions at different pH environments, and the detection capability in the natural water environment indicated its practical application potential. The in-depth studies suggested that the mechanism of the fluorescence quenching against antibiotics involved internal filtration effect and photoinduced electron transfer.