Linker-directed modulation of cerium metal-organic frameworks for tunable redox sensing and biomimetic catalysis

This work presents the rational synthesis of linker-engineered cerium-based metal-organic frameworks (Ce-TMA and Ce-TPA) via a facile room-temperature route and elucidates their structure-dependent multifunctional performance in fluorescence sensing, electrochemical detection, and nanozyme catalysis. Ce-TMA nanorods exhibited pronounced fluorescence turn-on behavior toward ascorbic acid (AA), delivering a ∼12-fold enhancement with an ultralow detection limit of 0.042 ppm in H₂O/CH₃CN (1 : 1), while maintaining excellent selectivity against competing reductants. Comprehensive mechanistic studies reveal that ascorbic acid induces selective Ce⁴⁺ → Ce³⁺ reduction and oxygen vacancy generation within the Ce-TMA framework, modulating ligand-to-metal charge transfer and suppressing non-radiative decay pathways, as verified by XPS, FTIR, UV-vis, and DLS analyses. Ce-TMA further demonstrated efficient electrochemical ascorbic acid sensing with a sensitivity of 9.41 µA µM^-1 cm^-2 and a detection limit of 3.66 µM. In contrast, Ce-TPA showed superior phosphatase-mimetic activity toward 4-nitrophenyl phosphate hydrolysis with enhanced pseudo-first-order kinetics and recyclability. The distinct performance divergence between Ce-TMA and Ce-TPA highlights the critical role of the linker topology in governing cerium redox chemistry, defect formation, and catalytic accessibility. This study provides fundamental insights into linker-directed engineering of Ce-MOFs for multifunctional sensing and biomimetic catalytic applications.