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