Tuning graphitic domains in porous carbon for enhanced competitive adsorption of benzene over acetone: the critical role of graphitization in separation selectivity

Porous activated carbon offers tunable surface chemistry, developed porosity, and environmental compatibility, with its high surface area providing abundant active sites for volatile organic compound (VOC) adsorption. In this study, benzimidazole served as the carbon precursor and potassium ferrate as the activating agent. We innovatively utilized heat treatment time to precisely control the graphitization structure of the material, systematically revealing the mechanism by which the microstructural evolution of carbon-based materials affects competitive VOC adsorption behavior. When heat treatment duration extended to 4 h, the resulting BFC800–4 sample exhibited the highest graphitization degree, and the area ratio of sp²-C / (sp²-C + sp³-C) in its XPS data increased to 0.91. In benzene/acetone co-adsorption, BFC800–4 showed exceptional benzene selectivity (coefficient: 5.57), with benzene and acetone adsorption capacities of 5.29 and 0.95 mmol/g, respectively. Multiscale simulations (GCMC/DFT) reveal enhanced adsorption stems from π-π interactions between graphitized carbon planes and benzene. Simultaneously, the introduction of nitrogen‑oxygen functional groups disrupts carbon surface electron distribution, weakening these interactions. Therefore, developing porous carbon materials with high graphitization and low functional group content enables directional control of competitive adsorption selectivity. The synthetic strategy and established microstructure-adsorption relationship in this study provide a theoretical basis for benzene-VOC separation and advance functional carbon design.