Covalent organic frameworks-coated silk membrane for durably efficient oil/water separation

Abstract

Engineering surface chemistry can effectively improve separation performance of membranes. Herein, we propose a covalent organic framework (COF)-coated strategy to enhance hydrophobicity, corrosion resistance and stability of silk membrane via engineering surface chemistry. 1,3,5-triformylbenzene (TFB) and 1,4-p-phenylenediamine (PDA) are used as monomers dissolved in 1,4-dioxane and ethanol, respectively. Then the two solutions are mixed with pre-treated silk, transferred to an autoclave following heating and the LZU1-COF particles coated silk membrane (Silk@COF) is obtained. LZU1-COF particles are covered on the surface of silk, which enhance the stability, raise the hydrophobic function and rose petal effect of silk membrane. Meanwhile, water can be effectively prevented from penetrating into the pores of Silk@COF, and oil droplets are adsorbed and fall into the collector under the effect of gravity. Not only that, the Silk@COF with lotus effect (water contact angles, WCA = 159.1°) and petal effect exhibits oil/water separation efficiency >98%, especially for dichloromethane (99.65%). This work provides a sustainable and versatile solution for water treatment with excellent eco-friendliness and cost-effectiveness.