Two water-stable lanthanide metal-organic frameworks with oxygen-rich channels for fluorescence sensing of Fe(iii) ions in aqueous solution

The development of metal-organic framework sensors with excellent stability under harsh physical and chemical conditions is of great significance in practical applications. Two isostructural lanthanide-organic frameworks, Ln-MOF ({Ln(L)(H2O)(DMA)}n, {FJU-13-Ln, Ln = Eu, Tb } (H3L = 3,5-(4-carboxybenzyloxy)benzoic acid)), were found to display exceptional stability, not only being stable in both acidic and basic aqueous solutions (pH 3-11), but also maintaining good robustness in boiling water and after activation. Furthermore, the plentiful oxygen atoms in the oxygen-rich channels of FJU-13-Eu and FJU-13-Tb acted as Lewis base sites for sensing metal ions, exhibiting high sensitivity (Stern-Volmer constant, KSV = 2.03 × 104 M-1 for FJU-13a-Eu and KSV = 2.11 × 104 M-1 for FJU-13a-Tb) and low detection limits (1.41 μM for FJU-13a-Eu and 1.01 μM for FJU-13a-Tb) for Fe3+ ions. This suggests that the two Ln-MOFs are promising fluorescent sensors for Fe3+ ion detection.