A Eu-MOF/EDTA-NiAl-CLDH fluorescent micromotor for sensing and removal of Fe3+ from water

Abstract

This paper reports a novel bioinspired Pt-free three-dimensional (3D) EDTA (Ethylene Diamine Tetraacetic Acid)-functionalized Eu-MOF (Metal Organic Framework)-based fluorescent micromotor as an active self-propelled micromachine for detection, capturing, and removal of Fe³⁺ from water. This micromotor was composed of EDTA-NiAl-CLDHs (calcined layered double hydroxides)/MnO₂ and a Eu-MOF, with each component functioning differently. The outer fluorescent Eu-MOF layer acted as a fluorescent sensor for detecting Fe³⁺, while the inner EDTA-functionalized NiAl-CLDH/MnO₂ layer functioned as a functional unit for Fe³⁺ adsorption, as well as the buffer layer for the nucleation and growth of the Eu-MOF. MnO₂ served as a catalyst in decomposing H₂O₂ for self-propulsion of the micromotor. The obtained micromotor exhibited a circle motion form with an average speed of 56.9 μm s⁻¹ in 5 wt% H₂O₂. This EDTA-functionalized Eu-MOF-based fluorescent micromotor showed excellent selectivity, high sensitivity (Stern–Volmer constant K_sv = 1.3 × 10⁴ L mol⁻¹, and limit of detection LOD = 0.15 μM) and high adsorption capacity (the maximum equilibrium adsorption capacity q_max = 112 mg g⁻¹) for Fe³⁺. Therefore, the novel 3D bifunctional fluorescent micromotor combining the MOF, EDTA-functionalized CLDHs and autonomous motion is promising for the simultaneous detection/adsorption and removal of pollutants, expanding the potential resources for micromotors and providing an efficient option for water quality monitoring and wastewater treatment.