A recyclable fluorescent covalent organic framework for exclusive detection and removal of mercury(II)

Here, by virtue of the natural merits of covalent organic frameworks (COFs), we report the rational design of a novel reaction-based recyclable fluorescent COF for both sensing and removal applications. The design concept is demonstrated by constructing allyl together with hydroxy groups functionalized COF material, AH-COF, for the exclusive detection and effective removal of mercury (II): the densely and well-distributed allyl cooperated with hydroxy groups as the Hg2+ reaction receptor sites via forming unique mercury-containing product based on the specific mercury-promoted reaction, and the pi-conjugation structure as the signal sensor. The satisfactory detection performance of AH-COF was obtained in aspects of excellent uniqueness, high sensitivity, facile visualization, and real-time response. More fascinatingly, AH-COF can be easily recycled in the presence of NaBH4. Moreover, the effective Hg2+ removal from water and the easy recycling of AH-COF provides the potential prospect for actual applications. Furthermore, the solid-state NMR investigations overwhelmingly certified the privileged reaction between Hg2+ and the allyl in cooperation with hydroxy groups of AH-COF. This study not only shows the use of fluorescent COFs for both exclusive detection and facile removal of Hg2+, but also emphasizes a novel design concept for rational structure construction of functionalized COFs for Hg2+ remediation.