Multistimuli-responsive pyrene-based lanthanide (III)-MOF construction and applied as dual-function fluorescent chemosensors for trace water and vitamins molecules

Three novel isostructural 3D porous metal–organic frameworks (3D MOFs) Ln-TBAPy (Ln = Sm (1), La (2), and Nd (3); H4TBAPy = 1,3,6,8-tetrakis (p-benzoic acid)pyrene) were synthesized, encompassing a π-conjugated organic ligand with a pyrene functionality. In particular, the crystal structure of [Sm3 (TBAPy)2 ((μ2-H2O)2(OH)2]∙(guests) (complex 1) was determined by X-ray single-crystal diffraction and displayed excellent performance in luminescent, which featured the alb topology and remarkable multiple pores dimensions. The complex 1 was utilized to determine the pH-dependent and temperature-dependent fluorescence under multistimuli responses, which exhibits its unusual photophysical characteristics and outstanding stability under special conditions. Markedly, the complex 1 probe achieves ultra-sensitive turn-on detection of trace water in organic solvent dioxane, exhibiting an ultra-low detection limit of 0.005% (v/v). In addition, we have explored that it has excellent fluorescence detection selective effect on various biological small molecule vitamins. On the one hand, the complex 1 can sense Vit-B6 with unique fluorescent switch ‘turn-on-off’ behavior, based on the changing concentration of Vit-B6 in MOF channel and hydrogen bond between host–guest interaction. On the other hand, complex 1 has high sensitivity to the quenching of Vit-B9 and Vit-K3, with the LOD as low as 0.32 μM, and 3.94 μM, respectively. Our synthesis strategy of Ln-TBAPy MOF materials will play simultaneously multiple roles and open up an effective avenue to dual-function fluorescence sensor of water and biological small molecule vitamins.