Covalent post-synthetic modified metal-organic framework UIO-66-NH2-HNA for selective and sensitive turn-on detection of acetylacetone, S2−, and PO43−

A fluorescent probe named UIO-66-NH2-HNA was prepared by covalent post-synthetic modification of UIO-66-NH2. Experiments show that the fluorescence and structure stability of UIO-66-NH2-HNA can be maintained in a wide pH range of 1–12. UIO-66-NH2-HNA can act as a turn-on fluorescent probe to detect not only acetylacetone (acac), but also S2− and PO43−, and the detection limits are as low as 0.25, 0.083 and 0.069 μM, respectively. Further study on the mechanisms showed that the sensing mechanism of UIO-66-NH2-HNA for acac could be ascribed to donor–acceptor electron-transfer, and the detection mechanism for S2− and PO43− could be attributed to the framework collapse caused by the increase of pH. It is worth mentioned that UIO-66-NH2-HNA is the first MOF probe based on covalent post-synthetic modification of aldimine condensation reaction for the detection of acac by turn-on response.