Quaternary Ammonium-Mediated Delamination of Europium-Based Metal–Organic Framework into Ultrathin Nanosheets for the Selective Photoelectrochemical Sensing of Fe³⁺

Abstract

Structural delamination of bulk layered metal–organic frameworks (MOFs) remains a great challenge, largely owing to a lack of general synthetic strategies. Here, we reported a simple solvent-free intercalation strategy for the delamination of rare-earth-based MOF (RE-MOF) with a topology structure of MIL-78 by tuning the chain length of quaternary ammonium salts. Four types of quaternary ammonium salts, involving tetraethylammonium bromide (TEAB), tetrapropylammonium bromide (TPAB), tetrabutylammonium bromide (TBAB), and hexadecyl trimethyl ammonium bromide (CTAB) were introduced to investigate their intercalation capabilities. It is evident in our case that the interruption/intercalation behavior of quaternary ammonium salts differs with their steric structures, and the chain-like CTAB can induce obvious delamination of MIL-78 crystals. Particularly, the CTAB-intercalated ultrathin Eu-based MIL-78 nanosheets exhibited unique selective photoelectrochemical sensing property toward trace amounts of Fe3+ ions in aqueous solution with a detection limit of 0.0899 μM at a signal-to-noise ratio of 3. These results demonstrated a green bottom-up strategy to obtain high-quality RE-MOF nanosheets for potential photocurrent response applications.

Regulating the Porosity of Uranyl Phosphonate Frameworks with Quaternary Ammonium: Structure, Characterization, and Fluorescent Temperature Sensors

“…Template reagents of different sizes and structures affect the pore structure of MOFs . Li et al achieved structural stratification in rare-earth-based MOFs by introducing quaternary ammonium ions with different chain lengths . Intercalation behaviors are tuned by the spatial structures of ammonium ions, and CTAB with the longest chain can lead to the most significant stratification of MIL-78 crystals.…”

“…34 Li et al achieved structural stratification in rare-earth-based MOFs by introducing quaternary ammonium ions with different chain lengths. 35 Intercalation behaviors are tuned by the spatial structures of ammonium ions, and CTAB with the longest chain can lead to the most significant stratification of MIL-78 crystals. Therefore, using quaternary ammonium templates may afford a lesson for structure tuning of UPFs.…”

Mechano-thermochemical synthesis of rare-earth metal–organic frameworks with solvent-free coordination for visible and near-infrared emission

“…The rare earth metal centre in this structure is coordinated to six water molecules in addition to the carboxylic acid groups from the three ligands. Then, the components of the La(BTC)Á6H 2 O structure gradually decrease to disappear with lanthanide contraction, and the MIL-78(Y) (CCDC 1109360 †) [29][30][31] (the characteristic peaks are marked in Fig. 4a with a yellow background and the coordinated structure is shown in Fig.…”

“…The extraordinary water stability of the TJU-66 series materials provides them with potential for applications such as trace detection, molecular identification, potential fingerprinting, etc. 23,30,31 The TJU-66 (RE/Sc) (RE= Sm, Eu, Tb or Dy) with bright visible light emission was dispersed in water for 90 days. The PXRD patterns and FTIR absorption spectra show no significant changes in structure (Fig.…”

Novel Lanthanide-Based Metal–Organic Framework Isomer as a Double Ratiometric Fluorescent Probe for Vanillymandelic Acid

“…Metal–organic frameworks (MOFs), constructed by self-assemble of organic ligands and metal ions or metal nodes, − have drawn increased attention due to their potential applications in gas storage, molecular separations, and chemical sensing, as well as catalysis . Especially, MOFs have attracted great attention in the field of ratiometric fluorescence sensing. − Considering that the luminescence of MOFs could originate from ligands, metal ions, the charge interaction between ligands and metal ions, and guest molecules, the multiple emission centers of MOFs can be mainly obtained by introducing single or multiple lanthanide ions, , luminescent guest molecules, , carbon dots, Ru­(bpy) 3 2+ , and different organic linkers, along with lanthanide-based MOFs (Ln-MOFs) with single organic ligand and lanthanide ions. , Among them, most of the strategies generally require a complex post-synthetic modification process; thus, Ln-MOFs that are synthesized directly can be constructed as an ideal ratiometric fluorescence platform.…”