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