Missing-Linker 2D Conductive Metal Organic Frameworks for Rapid Gas Detection

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Engineering

Background:

• Metal-organic frameworks (MOFs) offer structural diversity for applications like gas storage and catalysis.
• Chemiresistive gas sensing requires MOFs with both electrical conductivity and optimal gas adsorption.
• Current MOF applications in gas sensing are limited by these combined property requirements.

Purpose of the Study:

• To develop an effective chemical sensing strategy using defect-engineered, two-dimensional conductive MOFs.
• To investigate the impact of missing-linker defects on MOF properties for gas sensing applications.
• To enhance the performance of MOF-based chemiresistive sensors.

Main Methods:

• Synthesized amorphous Ni-HAB (aNi-HAB) via a ligand oxidation method to introduce missing-linker defects.
• Fabricated and tested aNi-HAB based chemiresistive gas sensors.
• Conducted transient current measurements and density functional theory (DFT) calculations.
• Evaluated isostructural 2D aM-HAB (M = Cu, Fe, Co) MOFs to confirm the generality of the approach.

Main Results:

• The amorphous Ni-HAB (aNi-HAB) with hydroxyl defect sites showed rapid adsorption/desorption of water molecules compared to crystalline Ni-HAB (cNi-HAB).
• The aNi-HAB sensor exhibited high sensitivity, selectivity, linearity, fast response/recovery, and excellent stability, further improved by Nafion functionalization.
• DFT calculations and isostructural MOF studies revealed that hydrogen bonding at defective sites is crucial for enhanced humidity response and tunable sensing properties.

Conclusions:

• Defect engineering via missing-linker incorporation is a general and effective strategy for tuning the sensing properties of conductive MOFs.
• The developed aNi-HAB material shows significant promise for advanced chemiresistive gas sensing applications.
• This approach provides a pathway for designing next-generation MOF-based sensors with tailored functionalities.