Multifunctional Eu-MOF for simultaneous quantification of malachite green and leuco-malachite green and efficient adsorption of malachite green.

Multi-target detection combined with in-situ removal of contaminants is a challenging issue difficult to overcome. Herein, a dual-emissive Eu-metal organic framework (Eu-MOF) was constructed by pre-functionalization with a blue-emissive ligand and post-functionalization with red-emissive Eu ions using a UiO-66 precursor. The fluorescence of the synthesized Eu-MOF is highly selective and sensitive toward malachite green (MG) and its metabolite leuco-malachite green (LMG), which are environmentally persistent and highly toxic to humans. The limit of detection of MG and LMG are 34.20 and 1.98 nM, respectively. Interestingly, the fluorescence of this Eu-MOF showed ratiometric but different responsive modes toward MG and LMG, which enabled the simultaneous quantification of MG and LMG. Furthermore, a paper-based sensor combined with the smartphone was fabricated, which facilitated not only the dual-channel detection of MG, but also its portable, visual, rapid, and intelligent determination. Furthermore, the high surface area of MOFs, together with the coordinate bonding interaction, π-π stacking, and electrostatic interaction sites, endows Eu-MOF with the efficient ability toward MG removal. This multifunctional Eu-MOF can be successfully used for trace detection, simultaneous determination of MG and LMG, as well as efficient removal of MG. Thus, it exhibits bright prospects for widespread applications in the field of food and environmental analysis.