Unveiling the porosity effect of superbase ionic liquid-modified carbon sorbents in CO₂ capture from air

Direct air capture (DAC) of CO₂ represents one of the most promising technologies to achieve negative carbon emissions. In this work, the superbase ionic liquids (ILs)-modified carbon substrates were developed for DAC of CO₂ by harnessing the strong CO₂ binding capability of IL and the ordered porous channels of the carbon supports. Detailed porosity analysis revealed that the IL with an aromatic cation and an oxygenate anion preferred to fill the micropores, and a thin layer was created on the surface of the mesopores. Strong π-π interaction between the IL layer and the carbon surface was disclosed by wide-angle X-ray scattering (WAXS) analysis, leading to enhanced thermal stability of the IL phase. For the same lL coating amount, the DAC of CO₂ evaluation revealed that a larger mesopore size and pore volume in the carbon/IL composite materials led to higher CO₂ uptake capacity by exposing more active sites to integrate CO₂ from diluted sources. The thermodynamic analysis confirmed the critical role of IL coating in providing strong chemisorption sites and significantly improved selectivity to enrich the diluted CO₂ from the air atmosphere. This work provides guidance on leveraging the scaffolds' surface properties and porosities of the scaffolds to optimize DAC of CO₂ behavior.