Smart MOF-on-MOF Hydrogel as a Simple Rod-shaped Core for Visual Detection and Effective Removal of Pesticides

The immoderate use of pesticides in the modern agricultural industry has led to the pollution of water resources and ultimately threatens the human body. Herein, two metal-organic frameworks (MOFs), namely {[Zn(tpt)(2)center dot 2H(2)O]}(n) (Zn1) and {[Zn-2(tpt)(2)(bdc)]}(n) (Zn2), (Htpt = 5-[4(1H-1,2,4-triazol-1-yl)]phenyl-2H-tetrazole), respectively, are constructed as smart materials for visual and on-site detection of pesticides and their removal from water. The exposed nitrogen-rich sites and high chemical stability make Zn2 a self-assembly core to further fabricate MOF-on-MOF-sodium alginate (ZIF-8-on-Zn2@SA) composite by wrapping ZIF-8 on the outside surface. Inheriting the excellent fluorescent emission of Zn2, the rod-like ZIF-8-on-Zn2@SA module exhibits naked-eye detection of thiophanate-methyl (TM) in real fruits and vegetables with a broad linear range (10-100 x 10(-6) m), a low limit of detection (LOD = 0.14 x 10(-6) m), and satisfactory recoveries (98.30-102.70%). In addition, carbendazim (CBZ), the metabolite of TM after usage in crops, can be efficiently removed from water by the ZIF-8-on-Zn2@SA (q(max) = 161.8 mg g(-1)) with a high correlation coefficient (R-2 > 0.99). Therefore, the portable ZIF-8-on-Zn2@SA sensing platform presents a promising candidate for monitoring and removal of pesticides, especially suitable for regions with serious pesticide environmental pollution.

Automated summary

The excessive use of pesticides in modern agriculture has resulted in water pollution and poses a threat to human health. In this study, two metal-organic frameworks (MOFs) were constructed as smart materials for the visual detection and removal of pesticides from water. The developed MOF-on-MOF-sodium alginate composite exhibited excellent fluorescent emission and could detect pesticides in fruits and vegetables with a wide linear range and low detection limit. Additionally, the composite efficiently removed the pesticide metabolite from water.