Alkoxy functionalized covalent organic frameworks for efficient oil/water separation

The massive discharge of oily wastewater and the frequent occurrence of oil spills have posed serious threat to human. Hence, it is important to develop functional materials and related methods to achieve efficient oil/water separation. Herein, a new superhydrophobic COF (named SCOF) was designed and successfully synthesized with functional alkoxy side chains at room temperature for the first time and was then applied to oil/water separation. By loading SCOF onto the fabric, the prepared superhydrophobic Fabric@SCOF membrane could effectively separate different oil/water mixtures, and the separation efficiency was higher than 99 %. Noteworthy, when separating immiscible CH₂Cl₂/water mixture, the maximum oil flux was 63,129 L m⁻² h⁻¹ and the separation efficiency reached 99.8 %. To the best of our knowledge, this was the highest oil flux of superhydrophobic COF-based membrane prepared on the fabric substrate for the separation of immiscible oil/water mixture only in gravity. By loading SCOF onto porous melamine sponge, the fabricated Sponge@SCOF could adsorb different oils, and the adsorption capacity for CCl₄ could reach 151 g/g. This work provides insights for the design and synthesis of novel functional COFs, and broadens the application of COF-based superhydrophobic composite in oil/water separation, which is of great significance for oily wastewater treatment and environmental remediation.