Engineering cotton fibers with zirconium metal-organic frameworks as a recyclable material for sensing and removing aflatoxins in water

The presence of aflatoxins in natural water bodies has been discovered in more and more countries and regions. The simultaneous removal and detection of aflatoxins are urgently needed to prevent and control their contamination. In this research, water-stable and luminescent zirconium metal-organic frameworks (Zr-LMOFs) were in-situ grown on natural cotton fibers. Then, the as-prepared Zr-LMOFs@Cotton was utilized as a recyclable dual-functional material for removal and detection of aflatoxins in aqueous solutions. The removal efficiency towards different AFB1 concentrations (25-100 µg/L) in irrigation water and rice vinegar reached 92% and 97%, respectively. The possible mechanism for efficient removal was investigated and attributed to the synergistic effect of π-π interactions and hydrophobic effect. The Zr-LMOFs@Cotton maintained more than 95% of its removal efficiency even after 10 cycles. Further, utilizing the Zr-LMOFs@Cotton for visual and semi-automatic removal of the most concerned AFB1 in water samples was verified. Also, the fluorescent Zr-LMOFs@Cotton has been combined with a microplate reader to explore a high throughput method for rapidly detecting aflatoxins. A low detection limit of 0.1 μg/L (0.32 nM) and a wide linear range from 0.05 to 20 mg/L was realized. The efficient quenching of Zr-LMOFs@Cotton by AFB1 resulted from both the inner filter effect and photoexcited electron transfer. The Zr-LMOFs@Cotton could accomplish the simultaneous removal and detection of aflatoxins in 5 min with simple and convenient operations. The excellent absorptivity, stable fluorescence, and easy renewability of the developed Zr-LMOFs@Cotton provides a cost-effective and environment-friendly material and strategy for simultaneously removing and monitoring aflatoxins in liquid samples.