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

• A MOF@iCOF@Tb composite is fabricated via in-situ polymerization and coordination. • The MOF@iCOF@Tb composite is used as sensitive fluorescence probe for NF detection. • The MOF@iCOF@Tb composite exhibits high NF capturing capacity. • The monitoring and capturing mechanism is also investigated via XPS spectra and DFT calculation. 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-NH 2 @TpTG Cl , is designed by combining a Zr-based metal organic framework, UiO-66-NH 2 , with a guanidine-based ionic covalent organic framework (iCOF), TpTG Cl . The UiO-66-NH 2 @TpTG Cl 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-NH 2 @TpTG Cl for the capture of antibiotics with polar functional groups, such as norfloxacin, is excellent. Tb 3+ ions are then assembled onto the UiO-66-NH 2 @TpTG Cl skeleton. With the addition of norfloxacin to the composite, strong coordination between the carboxyl group of norfloxacin and the Tb 3+ ions in UiO-66-NH 2 @TpTG Cl @Tb occurred, and the characteristic fluorescence emission of Tb 3+ ( 5 D 4 → 7 F 5 ) is enhanced by antenna and spatial confinement effect. Consequently, ratiometric fluorescence detection and capture of norfloxacin are realized using UiO-66-NH 2 @TpTG Cl @Tb. The linear detection range is 0.01–1 μM and the detection limit is 4 nM. Most importantly, UiO-66-NH 2 @TpTG Cl @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.