An efficient one-step condensation and activation strategy to synthesize porous carbons with optimal micropore sizes for highly selective CO2 adsorption

Abstract

A series of microporous carbons (MPCs) were successfully prepared by an efficient one-step condensation and activation strategy using commercially available dialdehyde and diamine as carbon sources. The resulting MPCs have large surface areas (up to 1881 m² g⁻¹), micropore volumes (up to 0.78 cm³ g⁻¹), and narrow micropore size distributions (0.7–1.1 nm). The CO₂ uptakes of the MPCs prepared at high temperatures (700–750 °C) are higher than those prepared under mild conditions (600–650 °C), because the former samples possess optimal micropore sizes (0.7–0.8 nm) that are highly suitable for CO₂ capture due to enhanced adsorbate–adsorbent interactions. At 1 bar, MPC-750 prepared at 750 °C demonstrates the best CO₂ capture performance and can efficiently adsorb CO₂ molecules at 2.86 mmol g⁻¹ and 4.92 mmol g⁻¹ at 25 and 0 °C, respectively. In particular, the MPCs with optimal micropore sizes (0.7–0.8 nm) have extremely high CO₂/N₂ adsorption ratios (47 and 52 at 25 and 0 °C, respectively) at 1 bar, and initial CO₂/N₂ adsorption selectivities of up to 81 and 119 at 25 °C and 0 °C, respectively, which are far superior to previously reported values for various porous solids. These excellent results, combined with good adsorption capacities and efficient regeneration/recyclability, make these carbons amongst the most promising sorbents reported so far for selective CO₂ adsorption in practical applications.