Fabrication of core-shell magnetic covalent organic frameworks composites and their application for highly sensitive detection of luteolin.

In this work, a novel core-shell structured magnetic covalent organic frameworks (denoted as FeO@TAPB-DMTP-COFs (TAPB, 1,3,5-tris(4-aminophenyl)benzene; DMTP, 2,5-dimethoxyterephaldehyde) was fabricated via a facile step-by-step assembly approach. The resulting material was characterized by transmission electron microscopy, powder X-ray diffraction, Fourier transform-infrared spectroscopy, X-ray photoelectron spectroscopy and voltammetric methods. FeO@TAPB-DMTP-COFs was further coated on the surface of glassy carbon electrode to construct an electrochemical sensor for the determination of luteolin. TAPB-DMTP-COFs with highly ordered porous structure not only provide more active sites, but also avoid the aggregation of FeO. Meanwhile, FeO magnetic nanoparticles can obviously accelerate the electron transport. Under the optimal conditions, the method displayed low detection limit (0.0072 μmol L), wide linear range (0.010-70 μmol L), and good recoveries (98.5-102.0%). Moreover, there are no significant effects from the interferents. The feasibility of this method was applied to trace luteolin in chrysanthemum tea and carrot. We consider this COFs-based porous material would become one of the most promising materials in electrochemical sensor.