Effect of hydrothermal pH values on the morphology of special microspheres of lignin-based porous carbon and the mechanism of carbon dioxide adsorption

The study reports the economic and sustainable syntheses of a lignin-based porous carbon (LPC) for CO 2 capture application. The pH values of hydrothermal solution affected the polymerization and aromatization of spheroidization, with morphological changes from blocky to microsphere. In addition, the reliable mechanisms of CO 2 adsorption were proposed by combining experiments with Gaussian16 simulations based on DFT. The electrostatic attraction of oxygen-containing functional groups and the diffusivity resistance of CO 2 in the pores are the key factors for the CO 2 adsorption. ​The carboxyl groups have the strongest electrostatic attraction to CO 2 . LPC-pH 1 has the highest carboxyl group content, possessing a CO 2 adsorption capacity of up to 5.10 mmol/g at 0℃, 1 bar. Furthermore, CO 2 diffusion resistance became a main factor as the adsorption temperature increases. The innovative combination of quantum chemical calculations and microscopic properties provides a viable pathway for an insight into the future control of lignin-based carbon formation.