Supramolecular β-cyclodextrin–aniline system: a new class of amine on solid support for carbon dioxide capture with high amine efficiency

Abstract

Carbon dioxide adsorption on a supramolecular system of aniline encapsulated into a β-cyclodextrin (β-CD) cavity is studied for the first time. The molecular level distribution of an amine on a solid support is achieved in the present system. The amine group of aniline is oriented towards the wider rim of β-CD and is favorably exposed to the gas stream, which results in its maximum utilization for CO₂ adsorption. The mechanism of the chemisorption is through the formation of bicarbonate with the primary amino group and the water molecule present inside the β-CD cavity, as evidenced from the high amine efficiency (0.85 mol CO₂ per mol of nitrogen) with dry carbon dioxide gas, which is close to the maximum reported value. The formation of C₆H₅–NH₃⁺⋯HCO₃⁻ inside the β-CD cavity is supported by molecular modeling and confirmed by NMR and Raman spectroscopy studies.