Ratiometric fluorescent sensor based on metal-organic framework for selective and sensitive detection of CO.

Carbonate ion (CO) is an anion essential for the maintenance of life activities and is of great importance to human health. Here, a novel ratiometric fluorescent probe Eu/CDs@UiO-66-(COOH) (ECU) was prepared by introducing europium ions (Eu) and carbon dots (CDs) into the UiO-66-(COOH) parent framework under the guidance of a post-synthetic modification strategy and used for the detection of CO ion in the aqueous environment. Interestingly, when CO ions were added to the ECU suspension, the characteristic emission of carbon dots at 439 nm was significantly enhanced, while the characteristic emission of Eu ions at 613 nm was reduced. Therefore, the detection of CO ions can be realized through the peak height ratio of the two emissions. The probe had a low detection limit (about 1.08 μM) and a wide linear range (0-350 μM) for the detection of carbonate. In addition, the presence of CO ions can cause a significant ratiometric luminescence response and resulted obvious red-to-blue color shift of the ECU under UV light, which will facilitate visual analysis by the naked eye.