One-pot synthesis of yolk–shell mesoporous carbon spheres with high magnetisation

A simple and novel route for the synthesis of monodisperse yolk–shell magnetic mesoporous carbon spheres (Fe3O4@void@C) via a ‘one-pot’ strategy for direct carbonisation and etching was developed. The synthesised materials were characterised by XRD, TEM, SEM, FT-IR, EDS, TGA, N2 sorption, and magnetic susceptibility measurements, and the ideal conditions for the synthesis of the Fe3O4@void@C spheres were systematically investigated. The morphologies and the saturation magnetisation values were observed to be strongly influenced by the composition of the solvent (ethanol–water) and the proportions of TEOS and formaldehyde used in the synthesis. The synthesised materials possessed a large average pore diameter (4.5 nm) and a magnetisation strength (62 emu g−1) greater than that of Fe3O4 itself. The performance of Fe3O4@void@C in the adsorption of pyrene was tested in aqueous solution, and fast adsorption rates (approximately 40 min to reach equilibrium) and high adsorption capacities (77.1 mg g−1) were observed. In addition, Fe3O4@void@C exhibited excellent reusability for the adsorption of pyrene over six adsorption–desorption cycles.