In this study, Li₂CO₃- and (Li–K)₂CO₃-based porous carbon composites were synthesized from terephthalic acid, lithium hydroxide and sodium hydroxide through calcination at different temperatures. These materials were fully characterized through X-ray diffraction, Raman spectroscopy, and nitrogen adsorption and desorption. Results showed that the excellent CO₂ capture capacities of LiC-700 °C and LiKC-600 °C were 140 and 82 mg CO₂ g⁻¹ at 0 °C and 25 °C, respectively. Additionally, it is calculated that the selectivity of LiC-600 °C and LiKC-700 °C with a CO₂/N₂ (15 : 85) mixture was about 27.41 and 15.04, respectively. Therefore, Li₂CO₃- and (Li–K)₂CO₃-based porous carbon materials could be used to effectively capture CO₂ with high capacity and high selectivity.