A green sorbent for CO 2 capture: α-cyclodextrin-based carbonate in DMSO solution.

Cyclodextrin (α-CD)/KOH pellet dissolved in DMSO was utilized to capture CO 2 . KOH has a dual function of enhancing the nucleophilicity of the hydroxyl groups on the α-CD rims and acting as a desiccant. 13 C NMR spectroscopy provided evidence for the chemisorption of CO 2 through the formation of organic carbonate (RO-CO 2 - ·K + ). This was supported by the spectral changes obtained using ex situ ATR-FTIR spectroscopy upon bubbling CO 2 . Activation of α-CD with NaH or bubbling with 13 CO 2 verified that chemisorption occurred solely via RO-CO 2 - ·K + rather than inorganic bicarbonate. Volumetric gas uptake demonstrated a sorption capacity of 21.3 wt% (4.84 mmol g -1 ). To the best of our knowledge, this is the highest chemisorption value reported to date for CD-based sorbents. DFT calculations of the Gibbs free energies indicated that the formation of RO-CO 2 - ·K + was more favoured at the primary carbinol rather than its secondary counterpart.