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

Abstract 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 π-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.