Coupled Low-Temperature Precarbonization and Activation for Constructing Ultramicropore-Dominant Coal-Derived Carbon Adsorbent for High-Capacity CO 2 Adsorption Capture

Porous carbons from thermochemical activation of heavy carbon feedstocks are promising cost-effective adsorbents for CO2 adsorption capture, in which constructing ultramicropores commensurate with CO2 kinetic diameter is pivotal for achieving high adsorption capacity. Chemical activation involving high-temperature carbonization and activation remains a prevailing route to preparing porous carbon with high specific surface area; however, uncontrolled intense etching reactions at high temperatures inevitably create excessively widened pores that are ineffective for CO2 adsorption, giving rise to limited CO2 uptake. Herein, we proposed a modified strategy coupling low-temperature thermal activation and precarbonization to selectively develop ultramicropores in coal-derived porous carbon. Enabled by this strategy, a high ultramicropore volume of 0.55 cm3/g was constructed, along with a smaller average pore diameter, surpassing the levels achievable by conventional high-temperature chemical activation methods. Statistical analysis of multidimensional structural characteristics reveals that small carbon crystallites formed via the primary thermal pyrolysis of aromatic sheets during low-temperature precarbonization play a key role in ultramicropore development by improving interfacial mass transfer and reactions during low-temperature activation. Benefiting from its well-developed ultramicroporosity, as-prepared porous carbon adsorbent delivers a CO2 uptake of 4.69 mmol/g at 25 °C and 1 bar, ranking among the highest values reported to date for porous carbon adsorbents. This work established a simple approach that markedly improves pore architecture by only adjusting carbonization and activation parameters, enabling rational adaptation to diverse application scenarios.