A green, rapid, scalable and versatile hydrothermal strategy to fabricate monodisperse carbon spheres with tunable micrometer size and hierarchical porosity

Monodisperse micron-grade carbon spheres (MCSs) (1.1–7.1 μm) were prepared via the hydrothermal carbonization of maltose with the addition of polyacrylic and inorganic acid. The synthesis could be accomplished in 3 h and still take effect at a large maltose concentration (∼800 g/L) or in tenfold enlarged experiments. This strategy was also applicable to form MCSs with good monodispersity for various carbohydrates including glucose, sucrose, soluble starch, xylan, glucan and barley starch. The simple H2O2 oxidation and calcination under static air atmosphere could introduce good surface meso- and macroporosity (average pore size of 4.2 nm, 79% of total pore volume) onto MCSs. The covalent grafting of porous MCSs with hyperbranched quaternized polymers was implemented in aqueous solution, via amidation with polyvinylamine and following amine-epoxy addition reaction with 1,4-butanediol diglycidyl ether. As ion chromatographic stationary phases, the modified porous MCSs rapidly accomplished the baseline separation of typical inorganic anions and carbohydrates with high efficiency and satisfactory stability.