Ultra-highly porous carbon from Wasted soybean residue with tailored porosity and doped structure as renewable multi-purpose absorbent for efficient CO2, toluene and water vapor capture

Abstract

Renewable and cost-efficient absorbent is of continuous interest to address the challenges induced by greenhouse gas and volatile organic chemicals (VOCs). Inspired by the needs for pyrolysis valorization of organic solid wastes, this work reported the synthesis of series of super-developed porous carbons with specific surface area and total pore volume up to 4293 m2/g and 2.52 cm3/g, respectively, via easily scalable KOH activation of pyrolysis char from waste soybean residue. By finely regulating the synthesis parameters, the resultants offered tunable porosity and surface chemistry for exceptionally high CO2/N2 selectivity (308 by Henry's Law at 298 K) and ultrahigh absorption capacity toward toluene (1587 mg/g under P/P0 of 0.99 and 25 °C) and water vapor (2187 mg/g under P/P0 of 0.9–1 and 25 °C). These features made them competitive candidates as physical absorbents for CO2 capture, VOCs removal and dehumidification. Furthermore, the CO2 molecules generally experienced adsorption at ultramicropores and doped sites, in addition to stacking in larger pore space under higher pressure. By contrast, the hierarchical porosity offered extensive surface and space for vapor adsorption, whilst those aromatic and oxygenic structures at surface may further interact with non-polar toluene and polar H2O, respectively. The current products can be envisioned with a broader application in gas separation given the findings here. Besides, conversion of solid char instead of directly the raw biomass waste is worthy of both academic and industrial focuses toward optimal valorization of biomass waste.