Abstract To properly address the threat of global warming, there is an urgent need to reduce CO2 from the atmosphere through the development of environment-friendly technologies. Therefore, capturing/storage and utilization of CO2 as a refrigerant for adsorption cooling/heating technologies have been gaining momentum in the last decades. This study focuses on the development of novel activated carbons (ACs) with extremely large pore volume and high surface area from environment-friendly and abundantly available biomass precursor seeking higher CO2 adsorption capacity. Four AC samples are synthesized from the two biomass precursor’s namely waste palm trunk (WPT) and mangrove (M) employing potassium hydroxide as an activating agent. The porous properties of the synthesized ACs are investigated from the N2 adsorption/desorption data. It is praiseworthy to elucidate that the highest surface area and pore volume for biomass-derived ACs (BACs) are obtained 2927 m2 g−1 and 2.87 cm3 g−1, respectively. CO2 adsorption characteristics are investigated using a high precision magnetic suspension balance unit at five different temperatures ranging from 25 to 70 °C with various pressures. The WPT-AC (C500)/CO2 pair shows the highest adsorption uptake as high as 1.791 g g−1 (excess adsorption) and 2.172 g g−1 (absolute adsorption) at 25 °C and 5.04 MPa, which is superior to any other ACs reported to date. To the best of our knowledge, porous properties and adsorption uptake of CO2 reported in this study are the up-to-date benchmarks. The results show that novel BACs/CO2 pairs possess remarkably high adsorption performance, which will contribute towards the advancement of various adsorption-based technologies.