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[Display omitted] • NH 2 of UiO-66-NH 2 covalent bonding linkage with CHO of TpTt-COF. • UiO-66-NH 2 attenuates the aggregation-caused quenching effect of TpTt-COF. • Benzene ring of TpTt-COF and tetracycline interact recognition by π-π stacking. • Fluorescence quenching via N/O of UiO-66-NH 2 @TpTt-COF and OH/ NH 2 of tetracycline. • LOD of 7.4 nmol/L and recoveries of 88.58–104.31% are achieved. Tetracycline residues are seriously hazardous to environment, it's urgent to develop sensors to detect tetracycline for environmental monitoring. A fluorescence sensor based on dual-emissions UiO-66-NH 2 @TpTt-COF (donate as UNT) composite is constructed by an interfacial growth method for detecting tetracycline. The import of UiO-66-NH 2 attenuates the aggregation-caused quenching (ACQ) of TpTt-COF, which endows UNT emitting strong dual-emissions of 452 nm and 575 nm. Tetracycline is recognized by UNT through π-π stacking and interacts with triazine N and deprotonated O of UNT through intermolecular hydrogen bonds. These interactions impede the excited state intramolecular proton transfer (ESIPT) and intramolecular charge transfer (ICT), and promote the photoinduced electron transfer (PET), inducing synchronous fluorescent quenching of the dual-emissions of UNT. The synchronous response of UNT enhances the specificity and displays excellent sensitivity toward tetracycline with a detection limit of 7.4 nmol/L. UNT is applied for the detection of tetracycline in soil and river water with recoveries of 92.96–98.44% and 88.58–104.31%, respectively. An optosmart sensing system has also been developed to enable visual detection of tetracycline. This work provides a novel synchronous response sensor for antibiotic detection and opens a new path for core-shell MOF@COF composites in the field of environmental monitoring. [ABSTRACT FROM AUTHOR]