Facile preparation of coal-based ultramicroporous carbon microspheres for selective CO2 capture

The basic structure of aromatic compounds that are abundant in coal is the carbonaceous precursor derived from carbon microspheres. However, it remains to be a huge challenge to prepare carbon microspheres using coal due to the complex construction and composition of coal. Herein, a simple and viable way to obtain coal-based microporous carbon microspheres was developed by means of ethanol pyrolysis and a sequential extraction strategy. The as-prepared carbon microsphere featured aspherical micron particles of a uniform size (0.6–1.6㎛), abundant O-functional groups, excellent thermal stability, high SBET(415.5–983.2 m²/g), and plentiful ultramicropores(63.15–72.72 %). The coal-based carbon microsphere exhibited a noteworthy CO₂ uptake (3.19–4.97 mmol/g at 273 K and 1.0 bar), acceptable CO₂/N₂ selectivity (IAST: 23–46) and moderate isosteric heats (20–32 kJ/mol). This synthetic strategy is important for the preparation of ultramicroporous carbon microspheres using coal, and the synthetic carbon microspheres have promising prospects for highly efficient CO₂ capture.