The selective catalytic removal of CO2 has great significance in environmental engineering and the chemical industry, and the development of efficient and smart materials to tackle the problems related to CO2 pollution is commendable. Herein, we report that, by facile carbonization of a g-C3N4 and chitosan mixture in N2, nitrogen-decorated hierarchically porous carbons (N-HPC-xs) enriched with a controllable number of basic sites could be obtained. The aggregation of the unique helix 2D carbon network of N-HPC-xs resulted in abundant formation of micro-meso-macropores in the synthesized structures, enabling high exposure and accessibility of basic sites. The outcome is excellent performance for CO2 capture (2.05–3.38 mmol g–1 at 0 °C, 1.0 bar, and 1.52–2.61 mmol g–1 at 25 °C, 1.0 bar) with high IAST (ideal adsorbed solution theory) CO2/N2 selectivity (83.8–111.3 at 0 °C and 71.2–88.2 at 25 °C). Meanwhile, the loading of Co2+ or Zn2+ to N-HPC-xs would result in formation of novel metal@N-HPC-xs catalysts that show superior catalytic effect in CO2 cycloaddition with epoxides at atmospheric pressure to afford cyclic carbonates. It is demonstrated that the N-HPC-xs and the catalysts derived from them have bright prospects for the capture and utilization of CO2 originated from industrial activities.