Beyond Monofunctionality: A Pyridinium-Derived Photochromic Zn-MOF with Tetracycline Detection/Degradation and Its Eu/Tb Hybrids for Visual Monitoring and Multi-Level Security

Although progress has been made in recognizing and degrading tetracyclines (TC), integrating multiple functions-including specificity, intrinsic photoresponsive behavior, targeted pollutant recognition/degradation, and designable luminescencewithin a single MOF platform remains a significant challenge. Most reported systems excel in specific functions but lack synergistic integration. To address this gap, the rational synthesis and multifunctional exploration of a novel zinc-based MOF (complex 1) was reported. Complex 1 successfully integrates photochromism with TC management functions, enabling fluorescence sensing (LOD = 0.72 μM) while achieving efficient degradation and adsorption (88.08%) driven by π-π stacking interactions, pore confinement and photoelectron transfer. To enhance functionality, post-synthetic modification (PSM) was employed to incorporate Eu³⁺/Tb³⁺ ions into complex 1, yielding Eu/Tb@Zn-MOFs hybrids. Strikingly, the Eu³⁺/Tb³⁺ doping preserved the parent complex's photochromic properties while introducing characteristic f-f luminescence, enabling dual photochromic-fluorescent responses. By bridging pyridinium-ligand chemistry with MOF-based rare-earth functionalization, this study advances the design of multi-responsive coordination materials. The synergistic integration of photochromism, luminescence and structural durability provides a versatile platform for next-generation anti-counterfeit technologies, fluorescence detection, dynamic optics and stimuli-responsive smart materials. This work provides a metal-specific design strategy for multi-stimuli-responsive materials and pioneers a modular approach to advanced anti-counterfeiting and environmental remediation technologies.