Effective strategy to fabricate ZIF-8@ZIF-8/polyacrylonitrile nanofibers with high loading efficiency and improved removing of Cr(VI)

ZIF-8@ZIF-8/PAN nanofibers were fabricated by the incorporation of zeolitic imidazolate frameworks (ZIFs) with electrospun polyacrylonitrile (PAN) nanofibers, and following by the in-situ growth of ZIFs onto the surface of the nanofibers. The abundant micropores and active sites of ZIFs supplied the effective adsorption and reduction to heavy metal ions of Cr(VI). The obtained novel nanofibers overcome the crystal agglomeration of ZIF-8 effectively and maintained the porous structures by the nanofibrous morphology of PAN and the evenly distributed ZIF-8, and thus exhibited relative higher surface area (871.0 m² g⁻¹) and excellent loading efficiency of ZIF-8 (82.9 %). As target adsorbate, Cr(VI) could be removed from aqueous media effectively with the maximum adsorption capacity (q_max) of 39.68 mg g⁻¹, and with better recyclability. Significantly, guided with the proposed feasible adsorption-reduction mechanism of Cr(VI), toxic Cr(VI) ions could be further reduced partially to the relative harmless Cr(III). Potentially, the present stable and advantageous approach to loading and growing metal organic frameworks (MOFs) onto electrospun nanofibers could be extended to other water-stable MOFs and to remove various heavy metal ions.