Oxygen-Rich Carbons Prepared by K2CO3 Activation of Phenolic Resin for Efficient CO2 Capture

Developing adsorbents with rapid kinetics and high adsorption capacity is essential for efficient CO2 capture. Herein, oxygen-rich porous carbons were synthesized from phenolic resin through K2CO3 activation. By systematically varying the activation temperature and K2CO3/precursor ratio, the evolution of pore structure and its influence on CO2 adsorption behavior were comprehensively investigated. The reaction between K2CO3 and the carbon matrix generated abundant micropores while preserving oxygen-containing surface functionalities, leading to enhanced adsorption affinity toward CO2 molecules. The optimized carbon exhibited a high specific surface area of 1065 m2 g−1 and a narrow micropore volume of 0.54 cm3g−1, delivering equilibrium CO2 uptake capacities of 5.48 and 3.92 mmol g−1 at 0 and 25 °C under 1 bar, respectively. In-depth analysis revealed that narrow microporosity played a more dominant role than total surface area in determining adsorption performance. Moreover, the optimized adsorbent showed a CO2/N2 selectivity of 15; rapid adsorption kinetics, with 90% of equilibrium capacity achieved within 4.5 min; and a dynamic CO2 capture capacity of 0.91 mmol g−1. The moderate isosteric heat of adsorption (20–36 kJ mol−1) and excellent cyclic stability further confirmed the physisorption-dominated nature of the process. This work highlights the synergistic role of ultramicropore engineering and oxygen-containing surface functionalities in designing efficient porous carbon adsorbents for carbon capture.