Eu-MOF and Bifunctional AgI@Eu-MOF Composite for Fluorescence Sensing and Photocatalytic Degradation of Tetracycline

The integration of tetracycline (TC) detection and treatment within a single system is significant but challenging. This work presents a 3D Eu-based metal-organic framework (Eu-MOF) and its AgI@Eu-MOF composite, both of which serve as fluorescence turn-off sensors for monitoring TC, exhibiting high sensitivities with limits of detection (LODs) of 74.9 nmol·L^-1 (nM) and 0.117 μM, respectively. The TC concentration (<i>C</i>_TC) can be quantitatively determined using the linear fitting equations (<i>I</i>₀ - <i>I</i>)/<i>I</i> = 3.828 × 10⁴<i>C</i>_TC for Eu-MOF with <i>C</i>_TC = 9.9-90.9 μM and (<i>I</i>₀ - <i>I</i>)/<i>I</i> = 2.1576 × 10⁴<i>C</i>_TC for AgI-30@Eu-MOF with <i>C</i>_TC = 9.9-74.1 μM. The fluorescence assays using Eu-MOF and AgI@Eu-MOF were applied to lake water and tap water, whose measured <i>C</i>_TCs were very close to the spiked <i>C</i>_TCs, and the fluorescence recoveries were around 100%, supporting the accuracy and reliability. AgI@Eu-MOF loading 30 wt % AgI (AgI-30@Eu-MOF) was also a photocatalyst for TC photodegradation with a removal efficiency of up to 83.87%, a photocatalytic reaction rate of 0.0466 min^-1, and a stable recyclability in five cycles. The TC photocatalytic degradation of AgI-30@Eu-MOF was proposed as a Z-type heterojunction mechanism with the generation of ^•O₂^-, h⁺, and ^•OH free radicals. The AgI@Eu-MOF provides a solution for TC detection and treatment by integrating a fluorescence sensor and photocatalyst within a single system.