Facile fabrication of hydrophobic covalent organic framework decorated melamine sponge for efficient separation of immiscible oil-water mixture and water-in-oil emulsion

Frequent oil spills and oily sewage have caused serious environmental problems. Sponges have attracted great attention in oil-water separation due to their low cost and high porosity, but it still remains challenge to hydrophobic modification of sponge in facile and scalable manner. Here is reported a facile fabrication of porous and hydrophobic sponge composite (MS@COF) with effective oil-water separation by in-situ growth of hydrophobic TFB-BD(Me)2 COF on the surface of melamine sponge. Combining the porous structure of the sponge and hydrophobicity of COF, the composite can separate oil-water mixture and water-in-oil emulsions in a fast way. The prepared MS@COF showed oil adsorption capacity up to 160 g g-1. In addition, continuous separation of oil-water mixture was demonstrated using a peristaltic pump with a separation rate of 50 mL min-1. More importantly, the composite could separate surfactant-stabilized water-in-oil emulsions with separation efficiency of 98.8%. The oil-water mixture and oil-water emulsion separation ability of the composite persisted after 50 separation cycles thereby demonstrating good recyclability. The composite also showed good chemical stability, mechanical and flame retardancy. This work introduces a new approach for the synthesis of hydrophobic sponge decorated with COF nanoparticles for oily wastewater treatment and organic pollutant removal on water surfaces.