Targeted enhancement of ultra-micropore in highly oxygen-doped carbon derived from biomass for efficient CO2 capture: Insights from experimental and molecular simulation studies

•Highly oxygen doped porous carbons were prepared for CO2 capture.•Mechanical compaction treatment targets a 24 % increase in the volume of ultra-micropores.•The contribution of pore structure and functional groups is 62 % and 38 % at 1 bar, respectively.•The ultramicroporous carbon achieved high CO2 capture capacity of 5.6 mmol g−1.•The role of oxygen groups in CO2/N2 selectivity is stronger than that of pore structures. The preparation of efficient CO2adsorbents is crucial for CO2capture. Compared to polymer-basedcarbons and metal-organic frameworks(MOFs), biomass-basedcarbon exhibits lower adsorption performance. Here, we prepared high oxygen doped ultramicroporous carbon through hydrothermal treatment and mechanical compaction assisted KOH activation. The study found that mechanical compaction treatment can target a 24 % increase in the volume of ultra-micropores, resulting in a CO2capture of the prepared ultramicroporous carbon reaching 5.6 mmol g−1, which is 22 % higher than that of conventionally prepared porous carbon. Molecular simulation calculations roughly estimated that functional groups and pore structures contribute 60 % and 40 %, respectively, to CO2capture at 0.15 bar, and 47 % and 53 % at 1 bar. Meanwhile, we found that the selectivity of CO2/N2is mainly related to the trend of oxygen functional groups, and is not significantly correlated with the micropore volume smaller than 0.7 nm. Theoretical calculations revealed that the introduction of oxygen groups into porous carbon resulted in an increase in selectivity of over 150 %, which is stronger than the effect of pore structure. This work provides valuable theoretical and experimental support for the design, preparation, and application of adsorbents for capturing CO2in flue gas.