Zn-MOF74 as a “turn-on” fluorescent chemosensor for recognition and detection of water in acetone and Al3+ in ethanol with high selectivity and sensitivity

Abstract

Zn-based metal organic framework (Zn-MOF74) was prepared and well characterized. Zn-MOF74 is microporous crystalline framework and has high thermal and chemical stability. Zn-MOF74 displayed selective “turn-on” fluorescence enhancement response towards water in acetone and Al3+in ethanol. Water and Al3+ can induce the bright yellow-green and cyan fluorescence colors, respectively. The fluorescence intensity showed good linear relationship with water content in the range of 0–1.5% (volume percent) and with the concentration of Al3+ in the range of 0–200 μM, the detection limits were 0.045% for water and 0.61 μM for Al3+, respectively. In addition, Zn-MOF74 can be used to intuitively identify Al3+ by naked eyes in the form of test papers. Zn-MOF74 had good recovery of nearly 100% in the detection of Al3+ ions in practical water samples. The hydrogen bonding formation between H2O and O atom broke the coordination bonding between O atoms of hydroxyl on the MOF framework with Zn2+ ions, the electron distribution on MOF framework was changed and thus the fluorescence of MOF was obviously enhanced. The reversible fluorescence change, infrared spectra (IR) and x-ray photoelectron spectroscopy (XPS) demonstrated that fluorescence enhancement of Zn-MOF74 by Al3+ can be ascribed to the complex formation among them. Zn-MOF74 is a good candidate as “turn-on” fluorescence chemosensor for recognition and detection of water and Al3+ in different solvents.