(383j) Impact of Functional Groups on Porous Carbon Adsorbents and Strategies for Controlling Their Adsorption Affinity Toward Methane, Carbon Monoxide, and Carbon Dioxide

In accordance with global efforts to achieve net-zero emissions, the interest in development of advanced materials aimed at capture and separation of greenhouse gases has increased. Our research has focused on synthesizing an adsorbent that combines high adsorption uptake and cost-effectiveness for widespread industrial use. Herein, we introduce a one-step activation method using chlorinated polyvinyl chloride (cPVC) as a precursor, which is activated under different conditions by varying ratios of activation agent-to-cPVC and changing activation temperatures from 600 to 900 °C. This method not only facilitates the formation of micropores and functional groups within the adsorbent but also employs a variety of acids and oxidizing agents to modify the surface, introducing distinct functional groups that significantly influence the adsorption characteristics. By increasing the amount of KOH/cPVC, the textural properties of porous carbon exhibit an exceptional specific surface area and total pore volume of up to 3200 m²/g and 2.1 cm³/g, respectively. Notably, porous carbons with increased hydroxyl (-OH) content show higher adsorption uptakes for CH₄ and CO₂, while the affinity toward adsorbate has significantly decreased for the samples having a ketone (-C=O) functional group. The suggested synthesis approaches could facilitate ease of controlling functional groups on the carbon surfaces, and each impact on the functional group could be validated in the future through density functional theory (DFT) calculations.

Based on the experimental results, several porous carbon adsorbents having great potential for selectively capturing CH₄, CO₂, and CO could be successfully synthesized. Specifically, the samples exhibited a CO₂/CH₄ selectivity range of 3.3 to 7.3, which varied according to the functional group fractions. The applicability of these findings across various fields emphasizes the significant impact of our work and its contribution to advancing technologies that promote environmental sustainability.