Dynamic tailoring of the gradient porosity of biomass-derived porous carbons for highly effective CO2 capture

Abstract

Carbon capture has emerged as an efficient technology for mitigating the escalating atmospheric CO₂ levels. Porous carbons show promising potential for CO₂ capture by virtue of their tunable porosity and surface chemistry, while they typically exhibit limited capacity owing to the trade-off between high porosity and surface functionalization. Herein, we develop an innovative dynamic activation strategy with CuCl₂ as a porogen to construct biomass-derived hierarchical porous carbons (HPCs) with gradient porosity. This method not only enables the precise tailoring of pore size and surface heteroatom doping to synchronously achieve a high porosity and rich surface groups, but also allows for the recycling of porogens, aligning with green and sustainable chemistry principles. The optimized HPC material exhibits ultrahigh specific surface area (up to 2856.9 m² g⁻¹), well-interconnected micropores and satisfactory surface functional groups contents. Systematic investigations reveal that ultramicropores (<0.7 nm) dominate CO₂ adsorption at low pressures, while larger micropores and mesopores contribute more to capacity at high pressures. The optimal sample achieves superior CO₂ uptakes of 6.95, 4.32, and 2.07 mmol g⁻¹ at 273, 298, and 323 K under 1 bar, respectively, alongside a high CO₂/N₂ selectivity (up to 91 at 298 K). Furthermore, pyridinic-N and pyrrolic-N groups significantly improve selectivity, and meanwhile, the HPC materials demonstrate rapid adsorption kinetics and excellent cycling stability. This work not only advances the fundamental understanding of dynamic activation mechanisms but also establishes a sustainable pathway for designing porous carbon adsorbents for highly effective CO₂ capture.