Electron-bridge mediated Z-scheme nanozyme with homologous heterostructured MOF-on-MOF architectures for simultaneous colorimetric detection and removal of aflatoxin B1.

Mycotoxins are typical contaminants produced by various fungal species, showing significant risks to human health due to their wide distributions and high carcinogenicity. Herein, the homologous heterostructured MOF-on-MOF nanozyme with Z-scheme structure were constructed via surface-initiated strategy by encapsulation of Cu-BDC on HKUST-1 for simultaneous colorimetric analysis and removal of aflatoxin B1 (AFB1). The homologous Cu2+ ion plays a pivotal "electronic bridge" role in shortening the electron transfer distance between Cu-BDC and HKUST-1 and enhancing interfacial coupling. The recombination of intrinsic electrons and holes within HKUST-1@Cu-BDC can be suppressed owing to typical Z-scheme structure. These leads to a significant enhancement in peroxidase (POD)-like activity, as confirmed by advanced characterizations and density functional theory (DFT) calculations. Based on this enhanced homologous heterojunction, the indirect detection (HKUST-1@Cu-BDC/ssDNA biosensors) and direct removal (HKUST-1@Cu-BDC nanozyme) methods with limits of detection (LOD) of 0.87 μg/L and maximum removal rate of 79.6% for AFB1 have been established. Finally, the homologous MOF-on-MOF nanozyme was successfully verified by both detection and removal process in complex food samples, while also demonstrating excellent repeatability and stability throughout the tests. This work provides a versatile strategy in designing and fabricating high-quality Z-scheme heterojunction nanozyme for mycotoxins governance.