Superhydrophobic Self-Cleaning Composite of a Metal–Organic Framework with Polypropylene Fabric for Efficient Removal of Oils from Oil–Water Mixtures and Emulsions

Here, we report a metal–organic
framework (MOF) [Hf6O4(OH)4(TFNDC)6]·6H2O·2DMF [SHMOF, where
TFNDC = 1-(2,2,2-trifluoroacetamido)­naphthalene-3,7-dicarboxylate],
which possesses excellent chemical and thermal stability along with
remarkable hydrophobic characteristics. The hydrophobic SHMOF was used for in situ coating on the polypropylene (PP) fabric to
make a superhydrophobic SHMOF–PP fabric composite.
The immobilization of nanocrystalline particles of SHMOF creates a nanoscale hierarchy that enhances the hydrophobicity of
the material. The superhydrophobic SHMOF–PP composite
showed a water contact angle of 160°. The successful integration
of the MOF compound with PP fabric was confirmed using field-emission
scanning electron microscopy, X-ray powder diffraction spectroscopy,
Fourier transform infrared spectroscopy, and energy-dispersive X-ray
analysis experiments. Superhydrophobic SHMOF–PP composite displayed a high separation efficiency (93–99%)
for separating light, heavy, and crude oils from oil–water
mixtures. The flux for oil–water separation was found to be
13–18k L m–2 h–1. Importantly,
the SHMOF–PP composite can be used repetitively
up to a minimum of 20 times for oil–water separation. The recyclability
was also maintained in high acidic and alkaline media. Moreover, superhydrophobic SHMOF–PP composite showed excellent oil absorption
capacity (29–39 g/g) for heavy and light oils at ambient temperature.
A gravity-driven active-filtration process and separation against
the gravity process were also performed to examine the flexibility
of the composite for separation. We demonstrate that the SHMOF–PP composite has the merit of very high separation efficiency, absorption
capacity, good recyclability, and exceptional robustness, showing
high potential for versatile oil–water separation. Additionally,
the material displayed noticeable self-cleaning and antifouling properties.
The SHMOF–PP composite also exhibited good efficiency
(95–99%) and flux density (1845–1899 L m–2 h–1) for the separation of water-in-oil emulsions.