Dual-State\nRed-Emitting Zinc-Based MOF Accompanied\nby Dual-Mode and Dual-State Detection: Color Tonality Visual Mode\nfor the Detection of Tetracycline

Red-emitting\nmetal–organic frameworks (MOFs) are still mostly\nbased on the use of lanthanides or functionalization with red fluorophores.\nHowever, production of transition-metal-based MOFs with red-emitting\nis scarce. This work reports on the synthesis of a novel dual-state\nred-emitting Zn-based MOF (denoted as UoZ-7) with the capability to\ndetect target molecules in dual state, in solution, and as solid on\npaper. UoZ-7 gives strong red emission when excited in the solution\nand in the solid state with 365 nm ultraviolet (UV) lamp irradiation.\nCoordination-induced emission is the mechanism for the red emission\nenhancement in the MOF as a restriction of intramolecular rotation\noccurred to the ligand within the framework structure. UoZ-7 was successfully\nused for tetracycline (TC) using dual-mode detection, fluorescence-based\nratiometry, and color tonality, in the dual state, in solution, and\non the paper. TC molecules adsorb on the red-emitting UoZ-7 surface,\nand a yellow-greenish color emerges due to aggregation-induced emission\nbetween TC and UoZ-7. Concurrently, the inner filter effect diminishes\nthe red emission of UoZ-7. The dual-mode or dual-state detection platform\nprovides a simple and reliable fast method for the detection of TC\non-site in various environmental and biomedical applications. Moreover,\nred-emitting UoZ-7 will have further luminescence-based biomedical\napplications.