Fluorescent PU films for detection and removal of Hg2+, Cr3+ and Fe3+ ions

Highlights: • Boron dipyrromethene derivatives were first synthesized, and then introduced to prepare fluorescent macromolecular films. • The fluorescent macromolecular films remained the fluorescence as the boron dipyrromethene derivatives have. • The fluorescent films could detect Hg²⁺, Cr³⁺ and Fe³⁺ ions by the color change and fluorescence change sensitively. • Fluorescent macromolecular films could also separate Hg²⁺, Cr³⁺ and Fe³⁺ ions with high efficiency. Three small molecular boron dipyrromethene (BODIPY) derivatives (B3a, B3b and B3c) were well-designed and synthesized at first, and then were incorporated into polyurethane to obtain macromolecular fluorescent sensors. These small molecular BODIPY derivatives exhibited high sensitivity and selectivity to Hg²⁺, Cr³⁺ and Fe³⁺ ions. The colors of these chemicals changed rapidly upon the addition of Hg²⁺, Cr³⁺ and Fe³⁺ ions. In addition, their fluorescence peaks shifted and was enhanced as well. B3a, B3b and B3c still remained the sensing properties when being introduced to polyurethane (PU). The functionalized PU films not only showed color change and fluorescence shift for detecting Hg²⁺, Cr³⁺ and Fe³⁺ ions as their small molecular counterparts, but also triggered a new emission peak in 500–600 nm. Besides, the functionalized PU film (PU-B3a as a sample) could absorb Hg²⁺ ions more than 84 mg/g in unit time and volume. It suggested that as long as the structure of the small molecular sensor was remained, the fluorescent ability remained even it is introduced to the macromolecular chains. In addition, Glass transition temperature (T_g) of the PU films changed when B3a, B3b and B3c were introduced.