Capturing CO2 and subsequently converting into valuable chemicals has attracted extensive attention. Herein, a series of biomass-based N-rich porous carbon materials with high specific surface area and pore volume were prepared using biomass waste soybean dregs as precursors. The nitrogen content was up to 4 % with different forms in the carbon skeleton such as pyridine-N, pyrrole-N. The synergistic effect of ultra-micropore (pore size <0.7 nm) and N-containing groups endowed the materials with a high CO2 adsorption capacity, reaching 6.3 and 3.6 mmol g-1 at 0 and 25 °C under atmospheric pressure, respectively. In addition, the sufficient interaction between N-containing groups and CO2 was demonstrated by solid-state nuclear magnetic resonance spectroscopy, and the captured CO2 was possibly activated in the form of carbamate, which is conducive to subsequent conversion. Therefore, the supported catalyst with the as-synthetic porous carbon material as the carrier and ZnII as catalytic sites was prepared and successfully applied for carboxylative cyclization of propargylic amine with CO2 to afford the 3-benzyl-5-methyleneoxazolidin-2-one. The results showed that CO2 capture and in-situ conversion work effectively to produce highly value-added chemicals. In this process, the captured CO2 could be activated and fixed into chemicals in mild conditions. More importantly, the energy consumption in CO2 desorption and adsorbent regeneration could be avoided. The valorization of both solid waste and CO2 to valuable chemicals provides an elegant strategy of killing three birds with one stone.