Tunable internal structure carbon sphere synthesis driven by water-solubility and its application in gas separation

A method for synthesizing carbon spheres with a tunable particle size and internal structure from polyfurfuryl alcohol (PFA) was developed. By tuning the concentration of a structure directing agent (polypropylene glycol, PPG), we found a mechanism to tune the inner architecture of carbon spheres driven by water-solubility. A mixture of PFA and PPG transferred from the "water-in-oil" phase to an "oil-in-water" phase with an increasing content of PPG because of a difference in water-solubility between furfuryl alcohol (FA), PFA, and PPG. As a result, the internal morphology of the carbon sphere evolved from a "cheese-like" to a "pomegranate-like" structure, which was accompanied by an increasing specific surface area and pore volume. Furthermore, the separation of C₂H₂ and C₂H₃Cl was tested on the 25%-FACS (furfuryl alcohol-based carbon sphere) sample under different activation treatments with CO₂ or CO₂-NH₃, with the coexisting "cheese-like" and "pomegranate-like" inner structures, owing to its moderate pore volume and mechanical strength. The maximum adsorption capacity of C₂H₃Cl reached 0.77 mmol g^-1, while C₂H₂ was adsorbed in significantly lower quantities. It is believed that the high polarizability and high dipole moment of the C₂H₃Cl molecule primarily contribute to the excellent performance of C₂H₂ and C₂H₃Cl separation, and the introduction of polar N-containing groups on the carbon skeleton further promotes C₂H₃Cl adsorption.