Biomass‐derived carbon for CO ₂ capture is significant for reducing carbon emissions and recovering C1 resources, contributing to zero‐carbon goals. However, developing biomass‐based porous carbon with high CO ₂ capture while reducing regeneration energy consumption remains challenging. This study leverages the tunable pore structure and photothermal properties of biomass‐based carbon, integrating adsorption and solar‐driven desorption for efficient, low‐energy CO ₂ capture. Specifically, mechanical compaction increased the ultramicropore volume of the porous carbon by 25%, leading to a corresponding 25% enhancement in CO ₂ adsorption capacity. Theoretical calculations and correlation analyses further elucidated that ultramicropore volume, nitrogen doping, and oxygen doping play significant roles in CO ₂ adsorption. Under one‐sun illumination, the surface temperature of the prepared porous carbon rapidly rose to 57.1 °C within 6 min and stabilized around 71.0 °C, resulting in a regeneration efficiency of 75%. These findings provide valuable theoretical and practical insights for the development of high‐efficiency, low‐energy CO ₂ capture technologies.