Crystal engineering of novel MOF@iCOF composite as a multifunction platform for targeted monitoring and capturing of norfloxacin

Abstract

The construction of novel multifunctional nanocomposites is of interest because of their excellent proven detection and capture performance. Herein, a new type of porous material, UiO-66-NH2@TpTGCl, is designed by combining a Zr-based metal organic framework, UiO-66-NH2, with a guanidine-based ionic covalent organic framework (iCOF), TpTGCl. The UiO-66-NH2@TpTGCl retains the high crystallinity and hierarchical pore structure of the MOF and iCOF, and has a surface rich in guanidine groups, and hence it has excellent hydrophilicity and is rich in positively charged sites; thus, the potential capacity of UiO-66-NH2@TpTGCl for the capture of antibiotics with polar functional groups, such as norfloxacin, is excellent. Tb3+ ions are then assembled onto the UiO-66-NH2@TpTGCl skeleton. With the addition of norfloxacin to the composite, strong coordination between the carboxyl group of norfloxacin and the Tb3+ ions in UiO-66-NH2@TpTGCl@Tb occurred, and the characteristic fluorescence emission of Tb3+ (5D4→7F5) is enhanced by antenna and spatial confinement effect. Consequently, ratiometric fluorescence detection and capture of norfloxacin are realized using UiO-66-NH2@TpTGCl@Tb. The linear detection range is 0.01–1 μM and the detection limit is 4 nM. Most importantly, UiO-66-NH2@TpTGCl@Tb exhibits high capture capacity (251 mg g−1) and favorable capture efficiency (80.5%). Meanwhile, the mechanism is detailed explored through XPS spectrum and DFT calculation. We believe that this work will trigger the study of new iCOF-functionalized MOF composites and that it presents a promising strategy for simultaneous ratiometric luminescence monitoring and capturing of antibiotics from water.