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

Abstract

Covalent organic polymer nanosheets (COPNs) endowed with porous networks and large surface areas in their structures offer great advantages over other materials in addressing environmental problems. In this study, fluorine-free superhydrophobic COPNs were designed and applied to selective dye absorption. Notably, COPNs selectively adsorb dyes with a high hydrophobic index (HI) and reject low HI dyes with maximum adsorption capacities of 361 and 263 mg/g for crystal violet and methylene blue, respectively. The adsorption isotherm model showed that the COPNs follow the Langmuir adsorption isotherm model and pseudo-second-order kinetics. Next, we explored the superhydrophobicity of the COPNs by in situ fabrication with melamine sponge (COPNs–MS), which incorporates the superhydrophobicity of COPNs [water contact angle (WCA) of >150°] with the structure and flexibility of the MS skeleton. The COPNs–MS shows various oil-adsorbing properties with good adsorption capacity (from 60 to 120 g/g) and also effectively separates various surfactant-stabilized emulsions with a separation efficiency of over 99%. The as-fabricated COPNs–MS retains its superhydrophobicity in various solvents and hazardous conditions (WCA ≥ 150°) and exhibits good flame retardancy and excellent compression properties with excellent antifouling property due to the superhydrophobic COPN coating. Furthermore, COPNs–MS also demonstrates excellent recyclability because the strong COPN coating in the MS skeleton retains its hydrophobicity. Therefore, our fluorine-free superhydrophobic COPNs are not only capable of selective dye adsorption but also exhibit very good oil adsorption and surfactant-stabilized emulsion separation performance.

Tailoring Thiazole Decorated Polymer with Benzoselenadiazole for Enhanced SO2 Sensing

“…The disappearance of characteristics peaks in the FTIR spectra of BBTBSe at 2564 and 2227 cm –1 and the appearance of peaks at 1594, 1210, and 860 cm –1 , which correspond to the stretching frequencies of CN–C, N–C–S, and C–S–C, respectively, reveal the formation of thiazole ring in BBTBSe CP (Figure b). , Similarly, the FTIR spectrum of BBT shows the disappearance of characteristic peaks at 2564 and 2232 cm –1 and the appearance of signals at 1602, 1220, and 834 cm –1 , which correspond to the stretching frequency of CN–C, N–C–S, and C–S–C, respectively, revealing the formation of a thiazole (Figure S1b). − It was observed that CN and SH stretching frequency peaks disappeared, and new CN–C, N–C–S, and C–S–C stretching frequency peaks appeared in BBTBSe and BBT. These changes are ascribed to the successful formation of a thiazole ring in the CPs.…”

A facile approach to fabricating fluorine‐free superhydrophobic cotton fabric with excellent oil–water separation performance

“…The fabric showed good resistances to wear and water and high oil–water separation efficiency 21 . Nevertheless, in the preparation process of the reported superhydrophobic CFs, fluorine‐containing chemicals and harmful organic solvents are used, which is not beneficial for environment and ecology 22–24 . In addition, the superhydrophobic CFs are only able to remove oil, water and large particulate impurities, but unable to separate organic contaminants.…”

A robust COF@MXene membrane for ultra-high flux of water-in-oil emulsion separation

“…5,6 Many researchers have focused on combining commercially available porous substrates with polymers to prepare super-wetting separation membranes. 7,8 But both the membrane pore size and the stability of the polymers have become necessary considerations for separation. 9 Recently, a two-dimensional (2D) material-based membrane has emerged, and its precise layer spacing plays a key role in achieving excellent selective channels and high separation fluxes.…”