Epitaxial self-assembly of Bimetallic MOF heterostructure for fluorescent and colorimetric detection of tetracyclines

The irrational use of tetracycline antibiotics (TCs) leads to the pollution of environmental resources and finally threatens human health, which makes it urgent to develop a sensor for sensitively and selectively detecting the antibiotics. In this work, a Zn-based metal-organic framework (Zn-MOF) anchored on an amino-functionalized aluminum-based metal-organic framework (NH2-MIL-53(Al)) was constructed as a fluorescence sensor for TCs determination. The abundant –NH2 made NH2-MIL-53(Al) a self-assembly core, which facilitated the formation of MOF-on-MOF heterojunction by amide reaction with the exposed –COOH of Zn-MOF. The single characteristic emission peak of Zn-MOF-on–NH2–MIL-53(Al) at 402 nm could identify TCs by internal filtration effect. Upon introduction of TCs, Zn-MOF-on–NH2–MIL-53 (Al) enhanced the intrinsic fluorescence signal of TCs at 517 nm through the coordination via the metal active center (Zn (II)), forming a ratiometric fluorescent sensor with a reverse response. Zn-MOF-on–NH2–MIL-53(Al) sensor displayed excellent anti-interference capability with a broader linear range (0.1–80 μM), and a lower limit of detection (LOD) of 8.24 nM for tetracycline (TC), 2.77 nM for oxytetracycline (OTC), and 8.85 nM for doxycycline (DC), respectively. By merit of Zn-MOF-on–NH2–MIL-53(Al), a portable smartphone-integrated test hydrogel colorimetric platform was fabricated for visual colorimetric detecting TCs by incorporating the sensor with a smartphone. Additionally, the bimetal-organic framework smartphone sensing platform exhibited satisfactory recovery (95.66–107.65%) and reliability in beef, pork, and chicken. Accordingly, the tactics presented a new strategy for developing an integrated system for environmental pollutant detection.