In short, hierarchical porous carbons with the maximum pore diameter at around 1.5 and 5.0 nm were obtained from the direct carbonization of EP algae after the freeze-drying treatment for the first time. EPC-700 and EPC-900 separately has surface area of 452 and 417 m2/g, showing similar PSDs with small difference in the pores less than 1.0 nm. CO2 uptake is 9.0 and 28.6 wt% at 1 and 20 bar and 25 °C for the EPC-900. Due to the utilization of natural biomass precursor and low carbonization temperature, this method is considered as green and economic route, providing a simple sustainable way to obtain hierarchical carbons for potential adsorbents from algae biomass.