Dual-Channel Gas-Sensitive Fluorescent Switch: Realizing a Reversible Fluorescent Response to HCl and NH₃

Area of Science:

• Materials Science
• Chemistry
• Environmental Science

Background:

• Luminescent metal-organic frameworks (LMOFs) offer advantages for harmful gas detection over traditional materials.
• Existing LMOFs face challenges including limited stability, unclear fluorescence signal changes, and insufficient mechanistic understanding.

Purpose of the Study:

• To develop lanthanide metal-organic frameworks (Ln-MOFs) with rapid and reversible fluorescence "turn-on" responses to vapor exposure.
• To elucidate the dual-channel sensing mechanisms for HCl and NH3 vapors using experimental and computational methods.

Main Methods:

• Synthesis of two types of lanthanide metal-organic frameworks (Ln-MOFs): Ln-TCPE and Ln-ETTB.
• Gas vapor exposure experiments to observe fluorescence response (<5 s).
• Density Functional Theory (DFT) calculations to understand sensing mechanisms.

Main Results:

• Ln-TCPE exhibited a rapid (<5 s) and reversible "turn-on" fluorescence response to HCl vapor via a dual-channel mechanism (ligand conformation stabilization and Ln3+ coordination).
• This dual-channel mechanism resulted in a 780% fluorescence intensity increase and a 45 nm redshift.
• Ln-ETTB demonstrated "turn-on" detection of NH3 vapor solely through benzene ring locking, with excellent stability and recyclability.

Conclusions:

• This study presents the first report of dual-channel gas-responsive LMOFs.
• The developed Ln-MOFs offer rapid, reversible, and highly sensitive detection of harmful gases.
• Thorough mechanistic understanding through experimental and DFT studies paves the way for advanced LMOF-based gas sensing applications.