Hydrophobic MOF-808 particles encapsulated melamine sponge for efficient oil-water separation

Developing highly efficient adsorbents is one of the most feasible strategies to achieve oil-water separation. Herein, we exploited a new hydrophobic metal-organic framework (MOF) by a post-synthesis acid-exchange method. Pentadecafluorooctanoic acid (PFOA) was applied to substitute the acetic acid of MOF-808 to result in the fluorinated MOF-808-PFOA, which owns much larger water contact angle than the primary MOF-808. Further, we successfully loaded these sub-micron MOF-808-PFOA particles into a melamine (MA) sponge, via the crosslinking effect by polydimethylsiloxane (PDMS). The prepared MOF/PDMS/MA sponge shows a high contact angle of 151.9°, induced by the increased surface roughness of mesh filament and decreased surface energy. Meanwhile, it is found that this excellent hydrophobility remains well under different water media and pH values. Combining with the high hydrophobiclity, mechanical stability and porous structure, this sponge shows an excellent adsorption performance for various classes of organic oils, with the large saturated adsorption capacities (27–65 ​g ​g−1), short equilibrium time (∼3 ​s), and good recyclability. More interestingly, this sponge can serve as a filter cartridge to achieve the effective continuous oil-water separation, even under long-term use. Thus, our work provides a new sponge-based adsorbent for efficient oil-water separation, and proposes a feasible strategy to construct hydrophobic MOFs via post-synthesis methods.