Real‐Time In Situ Volatile Organic Compound Sensing by a Dual‐Emissive Polynuclear Ln‐MOF with Pronounced Ln^III Luminescence Response

Abstract

Lanthanide metal-organic frameworks (Ln-MOFs) are promising for luminescence detection of volatile organic compound (VOC) vapors, but usually suffer from the silent or quenched Ln 3 + emission. Herein, we report a new dual-emissive Eu-MOF composed of the coordinatively unsaturated Eu 9 clusters that afford abundant open metal sites to form a confined "binding pocket" to facilitate the preconcentration and recognition of VOCs. Single-crystal structural analyses reveal that specific analytes can replace the OH oscillators in the first coordination sphere of Eu 3 + and form a unique hydrogen-bonding second-sphere adduct tying adjacent Eu 9 clusters together to minimize their nonradiative vibrational decay. With the promoted Eu 3 + luminescence, the MOF realizes real-time in situ visual sensing of THF vapor (< 1 s) and shows a quantitative ratiometric response to the vapor pressure with a limit of detection down to 17.33 Pa. Also, it represents a topperforming ratiometric luminescent thermometer.

Highly Luminescent Lanthanide Metal‐Organic Frameworks with Tunable Color for Nanomolar Detection of Iron(III), Ofloxacin and Gossypol and Anti‐counterfeiting Applications

“…With the benefits of high quantum yields and long luminescence lifetimes, as well as characteristic peaks in the emission spectra, highly emissive lanthanide metal–organic frameworks (Ln‐MOFs) can be obtained by sensitizing the Ln 3+ emission with organic ligands and blocking the reverse energy transfer [12,13] . Ln‐MOFs usually feature large Stokes shifts, high detection selectivity, high sensitivity and fast response, and have become efficient sensing platforms for hazardous substances in recent years [14–16] . At present, a variety of MOFs were developed for Fe 3+ detection, but the detection limits mostly stay at the micromolar level, and highly efficient sensing materials for low nanomolar levels are yet to be developed [17–19] …”

Stable Europium(III) Metal–Organic Framework Demonstrating High Proton Conductivity and Fluorescence Detection of Tetracyclines

“…In terms of fluorescence emission properties, Eu­(III) and Tb­(III) ions have distinctive red and green characteristic emissions, respectively. , A significant quantity of MOFs based on these two ions are extensively used for fluorescence detection of various ions, small molecules, and bio-organic molecules. − Yao and co-workers reported a dual fluorescence-emitting Eu-MOF formed by the coordination-unsaturated Eu 9 clusters, which can realize real-time visual detection of THF vapor . For proton conductivity, in order to obtain highly conductive MOF materials, proton carrier molecules such as imidazole, phosphoric acid, and sulfonic acid can be introduced into the structure of porous MOFs. , In addition, functional groups with proton donating ability (-COOH, -OH, -PO 3 H, etc.)…”

Lanthanide Metal–Organic Framework Isomers with Novel Water-Boosting Lanthanide Luminescence Behaviors

“…To date, many significant efforts have been made to improve the emission efficiency of Ln 3+ ion, such as host–guest interactions, , the removal of dissolved oxygen, pressure-treated engineering, and the formation of hydrogen bonds, together with the replacement of the H 2 O ligand . Wu and co-workers designed a fluorescence sensor named Eu-HODA for methanol sensing by the turn-on mode.…”

“…To date, many significant efforts have been made to improve the emission efficiency of Ln 3+ ion, such as host−guest interactions, 22,23 the removal of dissolved oxygen, 24 pressuretreated engineering, 25 and the formation of hydrogen bonds, 26 together with the replacement of the H 2 O ligand. 27 Wu and co-workers designed a fluorescence sensor named Eu-HODA for methanol sensing by the turn-on mode. The emission enhancement mechanism was that hydrogen bond interactions between methanol and the terminal coordinated water molecules in the framework alleviated the O−H high-energy vibrations, resulting in the increase of luminescence intensity of Eu 3+ .…”