Systematic Optimization of N-Doped Hierarchical Porous Carbon from Liquefied Wood for Efficient Volatile Organic Compound Adsorption

Volatile organic compounds (VOCs) are hazardous air pollutants, and the development of sustainable carbon adsorbents with high capacity, humidity tolerance, and regenerability remains an important challenge. Herein, N-doped hierarchical porous carbons were synthesized from liquefied wood via melamine-assisted carbonization followed by a Na2CO3/K2CO3 activation strategy. By adjusting the Na/K ratio, the pore architecture and surface nitrogen configuration of the resulting carbons were systematically tuned. Among the prepared samples, BPC-Na5K5 exhibited the most balanced textural and surface properties, with a high specific surface area (2338 m2/g), a large micropore volume (1.117 cm3/g), and a substantial mesopore contribution (0.464 cm3/g). Under dynamic adsorption conditions, BPC-Na5K5 delivered a saturated toluene adsorption capacity (qe) of 592 mg/g at 25 °C and 1000 mg/m3 and retained 94% of its dry-state qe at 50% relative humidity, together with good regeneration stability. Binary VOC adsorption tests further demonstrated preferential toluene retention over acetone, ethyl acetate, and cyclohexane, accompanied by roll-up of the weaker adsorbates. Comparative analysis suggests that the superior performance arises from the cooperative effect of micropore-dominated adsorption space, mesopore-assisted mass transport, and surface chemistry that modulates aromatic VOC affinity. This work provides a practical mixed-carbonate tuning strategy for systematically optimizing hierarchical porosity and nitrogen configuration in liquefied-wood-derived porous carbons toward efficient VOC adsorption and removal.