Fabrication And Oil/Water Separation Performances Of Intelligent MOF Coatings With Special Wettability

The separation of oil/water mixtures becomes an urgent global challenge because of heavy oil leakages happened frequently and the increasing pressure on wastewater treatment.Recently,membrane materials with special wettability have obtained extensive attention due to their advantages including cost-effective,operational simplicity,environmentally-friendly,etc.However,most of membrane materials with special wettability for oil/water separation have been inevitably suffering from poor durability,and applicability.Therefore,developing membranes with superior durability is of great significance for practical applications.Besides,designing membranes with switchable wettability toward on-demand oil/water separation is conductive to improve their applicability.In this paper,two types of intelligent membrane materials were designed to meet the demand of actual separation process by fabricating MOF coatings with special wettability on stainless steel meshes.The main works are as follows:（1）A membrane with switchable wettability for on-demand oil/water separation was obtained by fabricating ZIF-L@8 coatings on stainless steel meshes via in-situ growth and heterogeneous epitaxial growth.Base on the two-dimensional leaf-shaped ZIF-L nanosheets,ZIF-8 nanoparticles were further grafted by heterogeneous epitaxial growth.The introduced ZIF-8 further enhanced the surface roughness and changed surface chemical composition,resulting in superhydrophilic and superoleophilic surface in air.The stainless steel mesh-supported ZIF-L@8 coating showed underwater superoleophobicity or underoil superhydrophobicity when prewetted by water or oil.The as-prepared membrane exhibited excellent separation performance for different series of oil/water mixtures with separation efficiencies of above 98.56%and fluxes as high as 12.56×10⁴ L·m^-2·h^-1.Moreover,cycles experiments of controllable oil/water separation process were explored and the prewetting induced controllable separation mechanism was further explained.Therefore,this ZIF-L@8 coating with switchable wettability is a processing alternative material for practical application in on-demand oil/water separation.（2）A self-healable superhydrophobic membrane for oil/water separation was prepared.The stainless steel mesh supported zeolitic imidazolate framework-7（ZIF-7）was fabricated by way of secondary hydrothermal growth,it was further modified by using coordinated polysiloxane elastomer（CPE）.The as-synthesized CPE-ZIF-7coating possessed a rough surface structure of microscale ravines with both superhydrophobicity and superoleophilicity,which could separate water-in-oil emulsions with separation efficiencies of above 99.9%and high fluxes of 1056L·m^-2·h^-1.The self-healing ability and working mechanism of CPE-ZIF-7-coating were explored by responding to continuous abrasion and O₂ plasma etching.In addition,the stabilities of CPE-ZIF-7-coated SSM were investigated with respect to various treatments including high temperature,corrosion and ultrasonication.Therefore,superhydrophobic CPE-ZIF-7-coating with fast self-healing ability would be a promising alternative material for practical application.