Microwave‐Assisted Solvothermal Synthesis of Covalent Organic Frameworks (COFs) with Stable Superhydrophobicity for Oil/Water Separation

Abstract

COFs were synthesized by a microwave-assisted solvothermal route, with the building blocks containing 1,3,5-tris(4-aminophenyl) benzene and 2,3,5,6-tetra-fluoroterephthalaldehyde (or 1,4-phthalaldehyde). The À F groups introduced into the benzene ring promoted hydrophobicity and stability of the COFs. The universality and long effectiveness of oil adsorption can be realized when applying COFs as adsorbent. The powder also exhibited excellent water-in-oil emulsions separation performance, with the separation efficiency no lower than 99.5%. In this work, the use of microwave solvothermal synthesis of superhydrophobic COFs is potential to replace the conventional synthesis process and more suitable for industrial scale-up production. Furthermore, the findings provide a new strategy for solving the problem of oil spill treatment and industrial water-in-oil emulsions separation by using the emerging 2D COFs.

Hydrophobicity Tuning in Isostructural Urchin-Shaped Covalent Organic Framework Nanoparticles by Pore Surface Engineering for Oil–Water Separation

“…Covalent organic frameworks (COFs) are layered two-dimensional/three-dimensional (2D/3D) materials characterized by a high surface area and good chemical stability. − The high surface area and the ability to functionalize the pore walls of COFs make them excellent candidates for oil–water separation, although this application still largely remains unexplored. Lately, a handful of reports have shown potential for using COFs as materials for oil–water separation. − However, a thorough investigation is needed to gain insight into the structure–property relationships that drive the oil–water separation ability and to chart the path for future materials development. Therefore, we hypothesized that the development of COFs composed of hydrophobic building blocks would be a straightforward synthetic strategy to produce promising oil sorbents without the need for postsynthetic material modification.…”

Superhydrophilic Modification of Polyvinylidene Fluoride Membrane via a Highly Compatible Covalent Organic Framework–COOH/Dopamine-Integrated Hierarchical Assembly Strategy for Oil–Water Separation

“…The current research on the application of COFs in oil–water separation mainly focuses on superhydrophobic modification, which display the advantages of high surface roughness, outstanding stability, and excellent separation efficiency. However, the superhydrophobic modification of COFs by fluorinated chemicals greatly increases the cost, − and the preparation of most hydrophobic COFs is complicated, time-consuming, and under harsh reaction conditions. , Thus, the development of inexpensive raw materials, simple preparation processes, as well as hydrophilic modification methods might be the focus of COFs applied in oil–water separation in future research. To the best of our knowledge, hydrophilic modification using COFs for oil–water separation needs to be studied.…”

Fluorine-Free Superhydrophobic Covalent-Organic-Polymer Nanosheet Coating for Selective Dye and Emulsion Separation

“…The as-prepared superhydrophobic MS composite showed an excellent oil adsorption retention capacity of over 93% for various solvents and oils with excellent recyclability. Later, Chen et al designed a microwave-assisted solvothermal synthesis of stable superhydrophobic fluorine-containing COFs for oil/water separation . However, their adsorption capacity was poor, even with fluorine functional groups in the COFs.…”

“…Later, Chen et al designed a microwave-assisted solvothermal synthesis of stable superhydrophobic fluorinecontaining COFs for oil/water separation. 41 However, their adsorption capacity was poor, even with fluorine functional groups in the COFs. Therefore, for a large-scale oil-spill recovery, long-term oil/water and emulsion separation technologies require highly ordered and stable porous materials.…”