Real-Time In Situ Volatile Organic Compound Sensing by a Dual-Emissive Polynuclear Ln-MOF with Pronounced LnIII Luminescence Response

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 Eu3+ and form a unique hydrogen-bonding second-sphere adduct tying adjacent Eu-9 clusters together to minimize their nonradiative vibrational decay. With the promoted Eu3+ 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 top-performing ratiometric luminescent thermometer.

Automated summary

In this study, a new dual-emissive Eu-MOF with coordinatively unsaturated Eu-9 clusters was reported, which provides abundant open metal sites to form a confined binding pocket for the preconcentration and recognition of VOCs. The MOF exhibits promoted Eu3+ luminescence, enabling real-time in situ visual sensing of THF vapor and quantitative ratiometric response to vapor pressure with a limit of detection down to 17.33 Pa. Additionally, it represents a top-performing ratiometric luminescent thermometer.