Naphthalene-grafted MOF as a unique fluorescent sensor for “turn-off” detection for Fe3+ and “turn-on” detection for ClO4- in different solvents with high selectivity and sensitivity

Abstract

Naphthalene-grafted zirconium-organic framework UiO-66 (HNA@UiO-66-NH2) was synthesized via the Schiff base reaction. HNA@UiO-66-NH2 retained the original crystal structure of UiO-66 and high thermal stability. HNA@UiO-66-NH2 exhibited fluorescence sensing ability in two modes, “turn-off” response to Fe3+ in methanol and “turn-on” response to ClO4- in ethanol with high selectivity and sensitivity accompanied by obvious changes of fluorescence color. Its fluorescence intensity presented linear changes with the concentrations of Fe3+ and ClO4- with low detection limits (LOD) were 0.911 μM for Fe3+ and 1.44 μM for ClO4-. In addition, HNA@UiO-66-NH2 can simply identified Fe3+ and ClO4- in the test paper mode with naked eyes. The photoinduced electron transfer (PET) from excited HNA@UiO-66-NH2 to Fe3+ ion and the absorption competition quenching (ACQ) were responsible for the fluorescence quenching, the fluorescence enhancement of HNA@UiO-66-NH2 induced by ClO4- was attributed to the hydrogen bond formation between HNA@UiO-66-NH2 and ClO4-. The satisfying accuracy in detection of Fe3+ in serum and the good recovery of HNA@UiO-66-NH2 in detection of Fe3+ and ClO4- in water samples confirmed the practical application capability. This work paved a way to fabricate the fluorescent sensing materials for the simple, accurate and instantaneous detection and recognition of the different analytes.