A Calixarene-Based Metal-Organic Framework for Highly Selective NO₂ Detection

Area of Science:

• Materials Science
• Chemistry
• Nanotechnology

Background:

• Metal-organic frameworks (MOFs) offer tunable porous structures for various applications.
• Calixarenes are versatile macrocyclic hosts with potential in molecular recognition.
• Developing selective sensors for environmental pollutants like nitrogen dioxide (NO2) is crucial.

Purpose of the Study:

• To synthesize and characterize a novel calixarene-based MOF (Zr-cal).
• To investigate the MOF's capability for visual detection and encapsulation of NO2.
• To evaluate the MOF's performance as a sensor material for NO2.

Main Methods:

• Synthesis and single-crystal X-ray diffraction of the calixarene-based MOF.
• BET surface area analysis to determine porosity.
• UV/Vis and IR spectroscopy for complexation analysis.
• Powder X-ray diffraction and 1H NMR spectroscopy for stability confirmation.
• Fabrication and testing of a home-made sensor cell.

Main Results:

• Successful synthesis of a 3D calixarene-based MOF with a gar topology and a BET surface area of 670 m2/g.
• Calixarene cavities within the MOF pores facilitate visual detection and encapsulation of NO2 via charge-transfer complexes.
• High selectivity and sensitivity for NO2 detection were observed.
• The material demonstrated good stability confirmed by spectroscopic and diffraction methods.

Conclusions:

• The synthesized calixarene-based MOF is a promising material for selective NO2 sensing.
• The MOF's porous structure and accessible calixarene units enable efficient NO2 capture and visual detection.
• This MOF represents a potential advancement in gas sensing technology for environmental monitoring.