Honeycomb-Like Nitrogen-Doped Ultramicroporous Biochar for Efficient and Robust CO2 Capture

• Biochar is synthesized by the one-pot carbonization-activation method from corncob. • Honeycomb-shaped biochar poses densely packed, nested, and compact ultramicropores. • Biochar shows graphite state with defects, functional groups, and sorption sites. • Remarkably high CO 2 sorption capacities reach up to 4.15 mmol/g at 1 bar and 298 K. • Biochar owns cyclic robustness with an attenuation rate of 13.98% over 20 cycles. Honeycomb-like nitrogen-doped ultramicroporous biochar for CO 2 capture is synthesized through various methods utilizing biomass, urea, and KOH as raw materials, nitridation agent, and porogen, respectively. The resulting materials meticulously undergo comprehensive characterization, revealing densely packed ultramicropores arranged in honeycomb-like patterns. The biochar predominantly exists in a graphite state of carbon with sufficient defects and abundant functional groups, along with a high nitrogen content, thereby providing numerous CO 2 sorption sites. High CO 2 sorption capacities are observed of 4.15 mmol/g (at 1 bar and 298 K) and 5.45 mmol/g (at 1 bar and 273 K) with sorption heat around 23 kJ/mol. The Sips model fitting displays satisfactory results at 298 K, indicating a maximum sorption capacity around 5.45 mmol/g, with regression correlation coefficients exceeding 0.9942. The sorption selectivity between CO 2 and N 2 is notably influenced by the surface nitrogen content present in the materials. These sorbents exhibit exceptional cyclic robustness during vacuum pressure swing cycles, with an attenuation rate as low as 13.98% over 20 cycles. The abundant availability and cost-effectiveness of biomass, combined with a straightforward synthesis procedure and excellent CO 2 sorption performance, position honeycomb-like N-doped ultramicroporous biochar synthesized through the one-pot carbonization-activation method as promising candidates for CO 2 capture applications. The honeycomb-like nitrogen-doped ultramicroporous biochar developed through the one-pot carbonization-activation synthesis method is preferred as a promising sorption material for CO 2 capture since the it predominantly exists in a graphite state of carbon with sufficient defects, abundant functional groups, high surface and bulk nitrogen content, and a large number of CO 2 sorption sites.