Preparation of ultramicroporous carbon for gas adsorption through oxygen-rich precursor-enhanced chemical activation

Abstract

The creation of ultramicroporous carbon with highly developed pore structures for CO₂ adsorption is a promising approach to addressing the challenges posed by CO₂ emissions. However, traditional activation methods often struggle with controlling pore development, making it difficult for porous carbon to achieve both high ultramicroporosity and a substantial specific surface area (S_BET), simultaneously. Herein, we introduce a scalable strategy that utilizes oxygen-rich precursors to enhance chemical activation, allowing for precise regulation of ultramicropores while ensuring sufficient pore development. Preoxidation in air results in a loose carbon structure, abundant active sites (oxygen-functional groups), and well-formed initial pores in the precursor. These features effectively facilitate the distribution of the activator and the etching of the carbon matrix, leading to the formation of new pores in the porous carbon. The ultramicropores measuring 0.65–0.7 nm in the porous carbon are selectively enhanced, with their volume increasing from 0.12 cm³/g to 0.26 cm³/g. Thanks to the high microporosity (84.27 %–91.07 %) and substantial S_BET (1589–2760 m²/g), the ultramicroporous carbon prepared through this strategy demonstrates impressive CO₂ uptake of 4.26 mmol/g (298 K, 1 bar) and 6.79 mmol/g (273 K, 1 bar), along with favorable regeneration economy (Q_st of 37.33 kJ/mol) and high CO₂/N₂ selectivity (S_ads of 56). This research offers valuable insights into the targeted regulation of ultramicropores and the design of porous carbon with outstanding CO₂ adsorption capabilities.