Synthesis of superhydrophobic and high stable Zr-MOFs for oil-water separation

A universal strategy is developed to construct a superhydrophobic and superoleophilic metal-organic framework (MOF) by an amidation reaction between amino group and acid chloride of octadecanoyl chloride. The introduction of long alkyl chain reduced the surface free energy, yielding a superhydrophobic Zr-MOF (UiO-66-NH-C18) with a high water contact angle (WCA) of 151.7°. The adsorbed amount of water on the UiO-66-NH-C18 was only 5.59 mmol/g, which was just 28 % of that on the UiO-66-NH 2 . More importantly, the hydrophobic modification improved the stability of Zr-MOFs under strong alkaline conditions (e.g., pH = 13). Furthermore, the UiO-66-NH-C18 can selectively absorb organic solvent from water and achieve continuous oil-water separation. The oil-water separation efficiency could reach up to 99.9 %. In addition, the UiO-66-NH-C18@sponge was also prepared through dip-coating of UiO-66-NH-C18 on the melamine sponge in the presence of PDMS solution. The resulting composite shows high adsorption capacities for various oils and organic solvents ranging from 32.3–66.1 g/g. The superhydrophobic UiO-66-NH-C18@sponge has potential as a promising absorbent for treatment of oily wastewater.