Preparation of a novel electrospun superhydrophobic magnetic CoFe2O4@TiO2/PVDF composite film with catalytic function and enhanced polar crystal content in PVDF

Superhydrophobic electrospun films for oil–water separation, particularly those with multiple functions such as magnetism, catalysis, and piezoelectricity, have received widespread attention. In this work, a novel electrospun superhydrophobic magnetic CoFe2O4@TiO2/polyvinylidene fluoride (PVDF) composite film was fabricated. Firstly, a CoFe2O4@TiO2 hybrid filler was prepared by a simple and effective solvothermal method, and its structure and magnetism were confirmed by different characterization techniques. Secondly, the electrospun CoFe2O4@TiO2/PVDF composite film was prepared and then modified with trimethoxy(1H,1H,2H,2H-heptadecafluorodecyl)silane (HFDS) to form the electrospun HFDS-CoFe2O4@TiO2/PVDF composite film. The resulting HFDS(2 wt%)-CoFe2O4@TiO2(30 wt%)/PVDF composite film was found to be superhydrophobic and could achieve oil–water separation by gravity filtration and direct absorption, with absorption capacities for valorous oils ranging from 7.7 g g−1 to 8.2 g g−1. The crystallinity degree of the polar piezoelectric β- and γ-form crystals of PVDF in the HFDS(2 wt%)-CoFe2O4@TiO2(30 wt%)/PVDF composite film was 25.1%, whereas the corresponding value of the pure PVDF solid film was only 14.3%. In addition, the HFDS(2 wt%)-CoFe2O4@TiO2(30 wt%)/PVDF composite film exhibited a magnetization strength of 0.69 emu g−1 at 20 000 Oe and could catalyze the degradation of Sudan Red dye. The multi-functional CoFe2O4@TiO2/PVDF composite film demonstrates its potential for various applications in oil–water separation and other fields.