Visible Light-Rectified Chemiresistive Sensing in Two-Dimensional Conductive Metal-Organic Frameworks

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Sensing

Background:

• Photo-activated chemiresistive gas sensors utilizing two-dimensional conductive metal-organic frameworks (2D c-MOFs) offer potential for low-power, real-time environmental monitoring.
• The precise influence of visible light on the sensing mechanisms of 2D c-MOFs towards different gas molecules is not well understood.

Purpose of the Study:

• To systematically investigate the gas-sensing behavior of four representative 2D c-MOFs under red and blue light illumination.
• To elucidate the underlying mechanisms governing the light-modulated sensing responses towards oxidizing (NO2) and reducing (H2S) gases.

Main Methods:

• Systematic gas-sensing measurements of four 2D c-MOFs exposed to NO2 and H2S under blue (400 nm) and red (620 nm) light.
• In situ Fourier transform infrared spectroscopy (FTIR) to analyze surface reactions.
• Density functional theory (DFT) calculations to confirm gas adsorption modes and electronic structure changes.

Main Results:

• A pronounced light-rectified sensing behavior was observed across all tested 2D c-MOFs.
• Both blue and red light generally enhanced NO2 detection while suppressing H2S detection, with blue light exhibiting a stronger effect.
• The NiPc-Cu-O MOF demonstrated sensitive and reversible NO2 detection (0.016 ppm LOD) under blue light at room temperature.

Conclusions:

• Visible light significantly modulates the gas-sensing properties of 2D c-MOFs, influencing charge transfer dynamics.
• The study reveals distinct photoinduced gas sensing behaviors and underlying mechanisms for 2D c-MOFs, paving the way for advanced applications.
• Light irradiation can enhance surface oxidation reactions and alleviate reduction reactions, crucial for understanding and optimizing gas sensor performance.