Multifunctional Lanthanide Metal–Organic Frameworks Based on –NH₂ Modified Ligand: Fluorescent Ratio Probe, CrO₄^2– Ions Adsorption, and Photocatalytic Property

In response to the growing concern for environmental pollution, two lanthanide compounds {[Ln(L)(H2O)]·4H2O}n (where Ln = Tb and Gd, H3L = 1-amino-2,4,6-benzene tricarboxylic acid) were synthesized using a -NH2 modified ligand and systematically characterized. Both compounds exhibit remarkable fluorescence response, adsorption of CrO42- ions, and photocatalytic degradation properties, as well as exceptional acid-base and thermal stability. Remarkably, the pH-dependent 1-Tb exhibits exceptional performance as a fluorescent probe for detecting Fe3+ and CrO42-/Cr2O72- ions in aqueous solutions, while also serving as a ratiometric fluorescent probe for the detection of Cr3+, offering rapid response, high sensitivity, selectivity, and recoverability advantages in application. Moreover, 1-Tb exhibits excellent detection capabilities and displays effective adsorption of CrO42- ions, with a maximum adsorption capacity of 230.71 mg/g. On the other hand, 1-Gd exhibits superior performance compared to 1-Tb in the photocatalytic degradation of antibiotics. The degradation mechanism is further elucidated by conducting experiments with DFT theoretical calculations.