A robust superhydrophobic and superoleophilic SA-HKUST-1 membrane for efficient oil/water mixture separation

Abstract

The metal–organic framework has great research value and application in oil–water separation, owing to its highly adjustable pore structure resulting from the combination of metal ions and organic ligands. In this work, the HKUST-1 membrane was prepared by an in situ growth method with purple copper mesh as the substrate, which showed superhydrophobic characteristics after stearic acid treatment. The surface morphology, chemical structure, and wetting behavior of SA-HKUST-1-CM were characterized by SEM, EDS, XRD, FTIR, XPS and contact angle tests. The results showed that the SA-HKUST-1-CM with rough micro–nano structures and low surface energy chemicals possessed superoleophilicity and superhydrophobicity (OCA = 0° and WCA = 154.6°). The membrane exhibited high separation efficiency (99%) and separation flux (2.36–6.85 × 10⁴ L m⁻² h⁻¹) for the five tested oils under gravity drive. It had outstanding chemical and mechanical stability under harsh environmental conditions. In addition, due to its excellent reusability, the separation efficiency remained over 97.5% after 20 repetitions of the separation experiment. The wettability mechanism of the SA-HKUST-1-CM was explained via the chemical bonding theory and capillary force-based separation model. The mechanism of oil–water separation was additionally clarified in relation to the liquid bridge system. This super wetting MOF membrane with a simple preparation method, low cost and excellent performance has great application value and potential for oil–water separation.