A Highly Sensitive Fluorescent Sensing Platform Utilizing Lanthanide Metal–Organic Frameworks for Total Antioxidant Detection

Total antioxidant capacity (TAC) reflects the collective ability of biological systems to counteract oxidative stress and is therefore an important indicator in redox biology, nutritional evaluation, and clinical assessment. Conventional TAC assays often suffer from insufficient sensitivity, pronounced matrix interference, and limited reliability in complex biological samples. Herein, we developed a redox-active lanthanide metal–organic framework (CeMOF@Tb) through mild aqueous-phase synthesis followed by post-synthetic incorporation of Tb3+ ions, serving as a luminescent probe for sensitive and reliable TAC analysis. The reversible Ce4+/Ce3+ redox couple serves as the antioxidant-responsive recognition unit, while Tb3+ provides a characteristic green luminescence output. The antioxidant-mediated reduction of Ce4+ to Ce3+ regulates the energy transfer process, thereby producing a concentration-dependent enhancement in Tb3+ emission and reduction in Ce3+ fluorescence. The sensing platform also exhibits high selectivity and strong resistance to interference from common coexisting species, supporting reliable TAC determination in complex biological matrices. Furthermore, the probe was applied to human serum samples, yielding recoveries of 91.6–122.6%. This study establishes an integrated redox-to-luminescence transduction strategy for TAC analysis and provides a versatile design framework for developing Ln-MOF-based probes for clinical biochemical applications.