Tunable Polyaniline-Based Porous Carbon with Ultrahigh Surface Area for CO₂ Capture at Elevated Pressure

Natural gas is the cleanest fossil fuel source. However, natural gas wells typically contain considerable amounts of CO₂, with on-site CO₂ capture necessary. Solid sorbents are advantageous over traditional amine scrubbing due to their relatively low regeneration energies and non-corrosive nature. However, it remains a challenge to improve the sorbent's CO₂ capacity at elevated pressures relevant to natural gas purification. Here, the synthesis of porous carbons derived from a 3D hierarchical nanostructured polymer hydrogel, with simple and effective tunability over the pore size distribution is reported. The optimized surface area reaches 4196 m² g⁻¹, which is among the highest of carbon-based materials, with abundant micro- and narrow mesopores (2.03 cm³ g⁻¹ with d < 4 nm). This carbon exhibits a record-high CO₂ capacity among reported carbons at elevated pressure (i.e., 28.3 mmol g⁻¹ total adsorption at 25 °C and 30 bar). This carbon also shows good CO₂/CH₄ selectivity and excellent cyclability. Molecular simulations suggest increased CO₂ density in micro- and narrow mesopores at high pressures. This is consistent with the observation that these pores are mainly responsible for the material's high-pressure CO₂ capacity. This work provides insights into material design and further development for CO₂ capture from natural gas.