CO2 capture by multivalent amino-functionalized calix[4]arenes: self-assembly, absorption, and QCM detection studies

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Analytical Chemistry

Background:

• Calixarenes are versatile macrocyclic hosts with tunable properties.
• Polyamino substrates are investigated for their ability to interact with small molecules.
• Carbon dioxide (CO2) capture and sensing remain critical areas of research.

Purpose of the Study:

• To investigate the reactivity of polyamino substrates, including calixarenes, with CO2.
• To understand how molecular structure influences CO2 capture efficiency and product composition.
• To explore the potential of these compounds in CO2 sensing applications.

Main Methods:

• Synthesis and characterization of tetraaminocalix[4]arenes, diaminocalix[4]arenes, and a gemini compound.
• Reaction of synthesized compounds with CO2 in chloroform.
• Analysis of reaction products using 1H and 13C NMR spectroscopy.
• Investigation of gas-solid reactions using Quartz Crystal Microbalance (QCM) measurements.

Main Results:

• All studied compounds react with CO2 to form ammonium carbamate salts.
• Tetraaminocalix[4]arenes efficiently form stable, self-assembled dimers.
• 1,3-Diaminocalix[4]arene shows reversible CO2 uptake, forming less stable zwitterionic salts.
• A QCM device utilizing 1,3-diaminocalix[4]arene demonstrated promising CO2 sensing capabilities.

Conclusions:

• The number, topology, and conformation of amino arms on calixarene scaffolds significantly influence CO2 reactivity and product formation.
• Specific calixarene derivatives exhibit potential for developing efficient CO2 capture materials.
• 1,3-Diaminocalix[4]arene is a promising candidate for developing QCM-based CO2 sensors due to its reversible CO2 affinity.