Non-Fluorinated and Robust Superhydrophobic Modification on Covalent Organic Framework for Crude-Oil-in-Water Emulsion Separation

Abstract

Covalent organic frameworks (COFs) having high specific surface area, tunable pore size and high crystallinity are mostly post modified following fluorine-based and complex synthetic approaches to achieve a bio-inspired liquid wettability, i.e. superhydrophobicity. Herein, a facile, non-fluorinated and robust chemical approach is introduced for tailoring the water wettability of a new COF-which was prepared through Schiff-base condensation reaction. A silane precursor was readily reacted with selected alkyl acrylates through 1,4-conjugate addition reaction, prior to grafting on the prepared C4-COF for tailoring different water wettability-including robust superhydrophobicity. The superhydrophobic C4-COF (SH-C4-COF) that displayed significantly enhanced (>5 times; from 220 wt. % to 1156 wt. %) oil-absorption capacity, was extended to address the relevant challenges of "oil-in-water" emulsion separation, rapidly (<1 minute) and repetitively (50 times) at diverse and harsh conditions.

Keywords: Covalent Organic Framework (COF); Selective Oil-Absorption; Superhydrophobicity; Surface Functionalization; Water-in-Oil Emulsion Separation.