Fluorescence sensing and adsorption removal of Hg²⁺ with sulfhydryl functionalized COF@MOF composite

A MOF@COF composite of network structure was fabricated by in-situ growth of imine-based COF (TPB-DVA-COF) on Zn-based MOF material (IRMOF) via a solvothermal procedure, then functionalized with sulfhydryl group through "click" reaction to give the novel multifunctional composite IRMOF@COF-SH. The IRMOF@COF-SH composite combined the properties of both MOF and Zn-based IRCOF, showing attractive fluorescence behaviors. The presence of Hg²⁺ induced the obvious quench of the fluorescence of the composite in pH range of 6-10, therefore a fluorescence sensing method was established for sensitive Hg²⁺ determination in the concentration range of 3-150 μmol/L, with a detection limit of 0.75 μmol/L. Moreover, the abundant sulfhydryl groups on the surface of IRMOF@COF-SH composite endowed it with excellent adsorption selectivity to Hg²⁺, with an adsorption capacity high up to 909.09 mg/g. The practicability of the IRMOF@COF-SH composite was well demonstrated by the accurate detection of Hg²⁺ contents in tap water with recoveries of 98.18 %-100.77 %, and the efficient adsorption removal of Hg²⁺ from simulated electronic waste liquid with removal efficiency high to 94.0 %.