Low-temperature and facile synthesis of N/O co-doped microporous carbon with tunable porosity and high heteroatom content for efficient CO2 capture.

The preparation of porous carbon with high specific surface area (SBET), favorable microporous characteristics, and appropriate heteroatom contents is crucial for efficient CO2 capture. However, conventional chemical activation typically involves high temperature and large amounts of corrosive chemical agents, resulting in excessive pore expansion and substantial heteroatom loss. Herein, we propose a novel air preoxidation-assisted sodium amide (NaNH2) activation strategy for cost-effective synthesis of N/O co-doped microporous carbon with superior CO2 uptake at low temperatures (400-600 °C). Results demonstrate that the pores, loose carbon frameworks, and high-density oxygen functional groups and defects induced by air preoxidation contribute to more thorough pore development and enhanced heteroatom doping in the precursor. Through further optimization of the activation temperature, Y500 combines large SBET (2018 m2 g-1), high microporosity (94.32 %) and ultramicroporosity (60.55 %), as well as appropriate heteroatom contents (N: 3.90 at.%, O: 16.12 at.%). Consequently, Y500 exhibits the highest CO2 uptake, reaching 3.58 mmol g-1 (298 K, 1 bar) and 5.77 mmol g-1 (273 K, 1 bar), along with high CO2/N2 selectivity (Sads = 125), suitable isosteric heat of adsorption (Qst = 31.99 kJ mol-1) and excellent kinetics. This work provides a new strategy for the preparation of N/O co-doped microporous carbon with excellent CO2 adsorption performance.