Pore Reorganization of Porous Carbon during Trace Calcium-Catalyzed Coal Activation for Adsorption Applications

Aiming to widely engineering the pore structure of porous carbons to obtain broadened adaptabilities toward various adsorption applications, we propose a catalytic activation strategy by introducing a trace amount of calcium-containing additive (≤1% weight ratio of coal) into the coal framework for synthesis of porous carbons with a wide tunability over pore configurations using a low-rank coal as stock. It is demonstrated that the loaded calcium species can catalyze the reactions between CO₂ and the coal framework, causing intense pore reorganization and development. Moreover, the pore configuration of the resulting porous carbons can be readily adjusted by changing calcium source types and doses, enabling the formation of microporous or hierarchically porous carbons. Evaluated as adsorbents, the as-obtained microporous carbon shows good CO₂ adsorption property with a capacity of 4.4 mmol/g and high selectivity for CO₂ against N₂ (85.6), while the hierarchically porous carbon demonstrates to be a promising candidate as an organic dye (Rhodamine B) adsorbent with a high rate and high capacity (786 mg/g within ca. 5 min). Considering the very small amount of calcium additives and the simple preparation process, this study offers a convenient and readily scalable way to make high-value use of the low-rank coal and a new strategy to control the porosity of porous carbons with broadened adaptabilities toward various adsorption requirements.