Turn-on fluorescent sensor based on curcumin@MOF-5 for the sensitive detection of Al3+

Two fluorescent chemosensors based on MOF-5 and curcumin (A-curcumin@MOF-5 and B-curcumin@MOF-5) were designed and synthesized. The two curcumin@MOF-5 materials retained the framework structure of MOF-5 and the fluorescence properties of curcumin. Importantly, both curcumin@MOF-5 materials in ethanol displayed highly selective fluorescence enhancement responses toward Al³⁺ with the special pore structure of MOF-5 as the main reason for the high selectivity. The fluorescence intensities of the two curcumin@MOF-5 materials showed a good linear relationship with Al³⁺ concentration with low detection limits of 3.10 μM for A-curcumin@MOF-5 and 2.84 μM for B-curcumin@MOF-5, respectively. The complexation of curcumin with Al³⁺ inhibited the photoinduced electron-transfer (PET) process and further enhanced the fluorescence of the curcumin molecules. Both the curcumin@MOF-5 materials can be used as fluorescent sensors to identify and detect Al³⁺ in water samples.