Hierarchical Ti-MOF Microflowers for Synchronous Removal and Fluorescent Detection of Aluminum Ions

Bifunctional luminescence metal-organic frameworks with unique nanostructures have drawn ongoing attention for simultaneous determination and elimination of metal ions in the aqueous environment, but still remain a great challenge. In this work, three-dimensional hierarchical titanium metal-organic framework (Ti-MOF) microflowers were developed by a secondary hydrothermal method for not only highly sensitive and selective detection of Al(III), but also simultaneously efficient decontamination. The resulting Ti-MOF microflowers with a diameter of 5-6 μm consisted of nanorods with a diameter of ∼200 nm and a length of 1-2 μm, which provide abundant, surface active sites for determination and elimination of Al(III) ions. Because of their substantial specific surface area and superior fluorescence characteristics, Ti-MOF microflowers are used as fluorescence probes for quantitative determination of Al(III) in the aqueous environment. Importantly, the specific FL enhancement by Al(III) via a chelation-enhanced fluorescence mechanism can be utilized for selective and quantitative determination of Al(III). The Al(III) detection has a linear range of 0.4-15 µM and a detection limit as low as 75 nM. By introducing ascorbic acid, interference of Fe(III) can be avoided to achieve selective detection of Al(III) under various co-existing cations. It is noteworthy that the Ti-MOF microflowers exhibit excellent adsorption capacity for Al(III) with a high adsorption capacity of 25.85 mg g-1. The rapid adsorption rate is consistent with a pseudo-second order kinetic model. Ti-MOF is a promising contender as an adsorbent and a fluorescent chemical sensor for simultaneous determination and elimination of Al(III) due to its exceptional water stability, high porosity, and intense luminescence.