A Phototautomeric 3D Covalent Organic Framework for Ratiometric Fluorescence Humidity Sensing

Area of Science:

• Photochemistry
• Materials Science
• Supramolecular Chemistry

Background:

• Photoinduced proton transfer is crucial for advanced materials but challenging to control in condensed phases.
• Excited State Intramolecular Proton Transfer (ESIPT) pathways require precise manipulation for functional applications.

Purpose of the Study:

• To design a novel 3D covalent organic framework (COF) for efficient and controlled photoinduced proton transfer.
• To develop a ratiometric fluorescence sensor for humidity detection with enhanced sensitivity and self-calibration.

Main Methods:

• Integration of a hydronaphthoquinone fluorophore into a crystalline, porous, phototautomeric 3D COF.
• Utilizing theoretical and spectroscopic studies to elucidate the ESIPT mechanism and tautomer dynamics.
• Demonstrating humidity sensing capabilities through fluorescence turn-on, emission redshift, and lifetime shortening.

Main Results:

• The 3D COF exhibits guest-induced fluorescence turn-on and emission redshift.
• Shortened fluorescence lifetimes were observed, enabling ratiometric sensing.
• The material demonstrated sensitive, rapid, steady, and self-calibrated humidity sensing across a wide range.

Conclusions:

• The phototautomeric 3D COF provides a robust platform for ratiometric fluorescence humidity sensing.
• The study offers molecular insights into designing functional porous materials for environmental and biomedical applications.
• Integration of host-guest recognition and photoelectronic response is key for multiplexed sensing.