Photocatalytic and Superhydrophobic Nanoporous Membranes for Emulsion Separation and Removal of Pesticides and Pharmaceutical Products

Metal organic framework (MOF)-derivatives have a larger specific surface area, higher porosity, tunable pore size, higher conductivity, good stability, more exposed active species, etc., but few literature are reported about their application potential in micropollutant separation and removal. In view of this, a robust MOF derivative-based photocatalytic superhydrophobic membrane (D6/TiO2/MoS2/NiCo-NC/PVDF) was successfully fabricated for the first time through solvothermal synthesis and chemical modification, combined with a negative pressure-assisted loading approach. (1) The MoS2-doping strategy effectively avoided the collapse and coarsening of cauliflower-like MOFs during the calcination phase and simultaneously ensured the uniform distribution of metal particles in MOF-derived carbons. (2) The synergistic catalysis of the NiCo-MOF derivative, MoS2, and TiO2 enhanced the transfer efficiency of electrons and free radicals, achieving efficient in situ degradation of pesticides and pharmaceutical and personal care products. (3) The introduction of sodium alginate greatly improved the adhesion between the coating and polyvinylidene fluoride (PVDF) membrane and simultaneously enhanced the growth of MOFs through complexation. (4) The cauliflower-like MOF-derived carbon skeleton with higher surface areas and micronanoporosity combined with a heterogeneous MoS2 structure provided a large specific surface area and enough adsorption sites for various pollutants. High thermal calcination treatment greatly enhanced MOF growth rate, thus resulting in a flaky structure with high regularity and a large specific area. (5) The ultralow surface energy of interlaced siloxane molecules endowed the hybrid membrane with robust superhydrophobicity and superoleophilicity, always maintaining superhydrophobicity after long-time photodegradation. The final membrane achieved continuous emulsion separation and a photocatalytic self-cleaning property. The separation efficiency of the hybrid membrane for emulsions was still up to 97% after reuse for 120 cycles, and it could degrade 86.5% PRO, 90.1% ACE, 92.1% ASP, and 94.3% SMZ, respectively, with the initial concentration of 10 mg/L. The driving forces for oil-water separation and decontamination of the D6/TiO2/MoS2/NiCo-NC/PVDF membrane mainly involved the grasping forces of dodecamethylcyclohexasiloxane, capillary force of inner pores, electrostatic interaction, hydrogen bond interaction, partial p-pi conjugation, van der Waals force, and lipophilicity.