Polyacrylonitrile/polybenzoxazine-based Fe3O4@carbon nanofibers: hierarchical porous structure and magnetic adsorption property

Abstract

Hierarchical porous, magnetic Fe₃O₄@carbon nanofibers (Fe₃O₄@CNFs) comprising graphitic nanofibers and embedded Fe₃O₄ nanocrystals were prepared by using electrospun polyacrylonitrile/polybenzoxazine (PBZ) nanofibers as composite carbon precursor. By the combination of precursor design and activation process, a series of Fe₃O₄@CNFs with a tunable porous structure including the surface area, pore volume and micro/mesopore ratio were obtained, and could achieve an extremely high surface area of 1623 m² g⁻¹ and a pore volume of 1.635 cm³ g⁻¹. Quantitative pore size distribution and fractal analysis were employed to investigate the hierarchical porous structure using N₂ adsorption methods and synchrotron radiation small-angle X-ray scattering measurements. The role of the precursor structure and activation treatment for the tuning of the porous structure and surface fractal dimension is discussed, and the relative fraction of closed and open pores in CNFs is confirmed. Furthermore, the as-prepared Fe₃O₄@CNFs exhibit efficient adsorption for organic dyes in water and excellent magnetic separation performance, which would make them a promising adsorbent for water treatment, and a new insight was also provided into the design and development of functional carbon nanomaterials based on PBZ precursor.