Preparation Of Hydrophobic Zr-MOFs And Sponge Composite For The Oil/Water Separation

Oil-water separation aims to solve the problems of industrial oil-containing wastewater and oil spill pollution.In this field,special wettable materials have received extensive attention.Metal organic framework materials(MOFs)show potential applications in water purification owing to their large specific surface area,large porosity,and adjustable pore size.However,due to their inherent structural characteristics,MOFs are sensitive and unstable to moisture in aqueous media,which limits their practicality.Hydrophobic modification of MOFs can effectively improve water stability.This paper focuses on the preparation of hydrophobic MOFs and their composite sponges for oil-water separation.The main research contents are as follows:(1)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-NHC18 was only 5.59 mmol/g,which was just 28%of that on the UiO-66-NH₂.More importantly,the hydrophobic modification improved the stability of Zr-MOFs under strong alkaline conditions(e.g.,p H=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 to99.9%.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 absorption capacities for various oils and organic solvents ranging from 32.3 g/g(n-hexane)–66.1 g/g(dichloromethane).The superhydrophobic UiO-66-NH-C18@sponge has potential as a promising absorbent for treatment of oily wastewater.(2)Synthesis of hydrophobic Zr-MOFs-F for oil-water separation:we report a one-pot synthesis of hydrophobic Zr-MOFs(Zr-MOFs-F)by adding 4-fluorobenzoic acid,which was used as the modulator and functionalized molecule.By adjusting the ratio of 4-fluorobenzoic acid to zirconium chloride in the preparation process,the wettability of MOFs was changed.Compared with the hydrophilicity of the original UiO-66(WCA=21°),UiO-66-1F(10)shew hydrophobicity(WCA=122°)and had high stability under acidic,alkaline and high temperature conditions.In addition,the superhydrophobic UiO-66-1F(10)@PDA@sponge composite was also prepared via dopamine polymerization and in suit grow of UiO-66-1F(10).The resulting composite shows high absorption capacities for various oils and organic solvents ranging from50.5 g/g(n-hexane)–107.8 g/g(dichloromethane)and good recyclability.