Potassium metaborate-activated boron-doped porous carbons for selective CO₂ adsorption

Growing environmental and efficiency concerns have driven significant interest in producing porous carbon from biomass while modifying its surface for selective carbon dioxide (CO2) adsorption. Designing microporous carbon materials with heteroatoms incorporated into the carbon framework has proven to be an effective strategy for enhancing CO2 uptake. In this study, for the first time, boron (B)-doped porous carbon was successfully synthesized through the pyrolysis of water chestnut shells (WSC) in the presence of potassium metaborate (KBO2), which acted as both an activating agent and a boron dopant source. This innovative approach leverages the dual functionality of KBO2 to simultaneously create a porous structure and introduce boron heteroatoms into the carbon framework. Pyrolysis was conducted at varying temperatures and mass ratios of KBO2 to WSC to optimize the textural and surface chemical properties of the synthesized porous carbons and enhance their CO2 adsorption capacity. The resulting B-doped porous carbons exhibited excellent structural characteristics, with a maximum surface area of 683 m2/g, a total pore volume of 0.30 cm3/g, and a boron doping level of up to 1.95 wt %. The optimal adsorbent demonstrated strong CO2 adsorption performance, achieving capacities of 3.15 mmol/ g at 25 degrees C and 4.22 mmol/g at 0 degrees C under 1 bar pressure. Additionally, the material exhibited high CO2/N2 selectivity, moderate isosteric heat of adsorption, rapid adsorption kinetics, excellent dynamic CO2 capture capacity, and outstanding cyclic stability. These properties make it a promising candidate for sustainable CO2 capture applications.