Dual-functional core-shell ZIF-8 with hierarchical pore compartmentalization: Simultaneous ratiometric fluorescence sensing and photocatalytic degradation of oxytetracycline.

A multifunctional composite, designated as ZIF-8@LY/ZIF-8@CDs-Eu3+, was rationally designed as a fluorescence probe and high-performance photocatalyst for simultaneous detection and degradation of oxytetracycline (OTC). To address the critical challenge of co-encapsulating fluorescein (LY) and Eu3+-functionalized carbon dots (CDs-Eu3+) within a single porous particle without functional incompatibility, we proposed a core-shell ZIF-8 architecture, where the etched ZIF-8 core served as the host for LY loading, and the in situ grown ZIF-8 shell was introduced to immobilize CDs-Eu3+. The acetic acid etching of the ZIF-8 core created abundant sites to absorb more LY molecules, which further enhanced the OTC removal efficiency. On this basis, a fluorescence "turn-on" ratiometric quantitative detection platform for OTC was established, with a low limit of detection (LOD) of 1.8 nM. Meanwhile, the ZIF-8@LY/ZIF-8@CDs-Eu3+ composite achieved 99% OTC removal within 300 min under light irradiation, driven by the generated reactive species including superoxide radicals (·O2-), hydroxyl radicals (·OH), and photogenerated holes (h+). Notably, three parallel degradation pathways of OTC were identified via high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS). This work not only provides an innovative strategy for the design of multifunctional MOF-based composites, but also opens a new avenue for the efficient monitoring and elimination of antibiotic residues in complex environmental matrices.