Hydrophobic Carbon with Abundant Defects and Nitrogen Enrichment Effectively Enhances Adsorption of Styrene: Experiments and DFT Calculations

Developing low-cost adsorbents with high selectivity and moisture resistance remains a critical challenge for the effective removal of volatile organic compounds (VOCs). Herein, a synergistic methanol supercritical pretreatment and nitrogen-doping strategy was proposed to fabricate lignite-derived N-doped porous carbons (PNCs). Comprehensive elemental analysis and structural characterization demonstrated that the sample prepared at a pretreatment temperature of 280 °C (PNC-280) achieved an optimal balance among the degree of defect, pore architecture, surface chemistry, and hydrophobicity. After supercritical treatment, PNC-280 exhibits a specific surface area of 1033 m2/g and the highest nitrogen content (5.82%). Even at 50% relative humidity, PNC-280 was still able to retain 80% of its styrene adsorption capacity (1329 mg/g). Density functional theory (DFT) calculations indicate that the adsorption energy of N–6 for styrene is −18.58 kJ/mol, while that for water is −5.43 kJ/mol, thereby reducing competition from water vapor and simultaneously increasing the affinity for styrene. This study offers a solution for enhancing the adsorption of styrene under humid conditions.