Fabrication of a core-shell structured MOF@COF fluorescent composite and its sensing performance toward nitrofurantoin

A novel core–shell structured NH 2 -MIL-88(Fe)@TFPT-Tt-COF composite was successfully constructed via an in situ growth strategy, enabling intimate interfacial bonding and synergistic effects between the MOF core and the COF shell. • The composite exhibits dramatically enhanced fluorescence compared to the individual MOF or COF, and acts as a “turn-off” sensor for nitrofurantoin (NFT) with an ultralow detection limit of 0.18 μg·mL −1 based on the inner filter effect. • The sensing platform features rapid response (equilibrium within 1 min), excellent selectivity against common metal ions and antibiotics, and good applicability in real samples with recoveries of 84.3%–107.6% in soil and lake water. • Offers a new strategy for applying MOF@COF heterostructures to the on-site, rapid, and sensitive detection of trace antibiotic residues in complex environmental matrices. A core-shell structured NH 2 -MIL-88(Fe)@TFPT-Tt-COF composite was successfully constructed via an in situ growth strategy, using NH 2 -MIL-88(Fe) as the core and TFPT-Tt-COF as the shell. The structure, morphology, and thermal stability of the composite were systematically characterized by Fourier transform infrared spectroscopy, powder X-ray diffraction, scanning/transmission electron microscopy, thermogravimetric analysis, and nitrogen adsorption–desorption measurements. The results confirmed the intimate interfacial bonding between the MOF core and the COF shell. Compared with the individual components, the composite displayed significantly enhanced fluorescence intensity. A fluorescent sensing platform based on this composite was developed, which enabled highly sensitive and selective detection of nitrofurantoin (NFT). Preliminary mechanistic studies revealed that the quenching effect mainly originated from a photoinduced electron transfer (PET) mechanism. The proposed method was applied to the spike recovery analysis of NFT in real samples such as soil and lake water, yielding recoveries ranging from 84.3% to 107.6%, with a limit of detection as low as 0.18 μg·mL −1 , demonstrating that the sensor possesses satisfactory accuracy and practicality in complex environmental matrices. This work provides a new strategy for the application of MOF/COF composites in the rapid detection of antibiotic residues in the environment. Download: Download high-res image (167KB) Download: Download full-size image