New strategy to prepare ultramicroporous carbon by ionic activation for superior CO₂ capture

Traditional chemical activation methods to prepare porous carbons adsorbents consume large amounts of activating agent through physical mixing. Herein, we developed a new strategy to prepare microporous carbons with uniform ultramicropores (∼0.57 nm) through ionic activation method by using potassium carboxylate as an activating agent, which was uniformly incorporated onto the surface of hydrothermally prepared hydrochar. The ultramicroporous carbon adsorbent developed by this new method showed high CO₂ uptakes of 5.87 and 3.82 mmol g⁻¹ at 0 and 25 °C, respectively. We demonstrated that small amounts of uniformly distributed potassium carboxylate contributed to the development of ultramicroporosity. This research paves the way for a new route to prepare ultramicroporous carbons as efficient CO₂ adsorbents by using significantly lower amounts of activating agents and hence the process may be not only cost-effective but also avoids negative impacts of traditional chemical activation.