Ultrathin Covalent Organic Framework Membranes Prepared by Rapid Electrophoretic Deposition

Abstract

Covalent organic frameworks (COFs) are a disruptive material platform for various novel applications including nanofiltration for water purification due to their excellent physicochemical features. Nevertheless, the currently available approaches for preparing COF membranes need stringent synthesis conditions, prolonged fabrication time, and tedious post‐processing, leading to poor productivity. Herein, a simple and efficient layer‐by‐layer stacking assembly strategy is developed based on electrophoretic deposition (EPD) to rapidly generate ionic COF membranes due to the uniform driving force for nanosheet assembly. A new two‐cell EPD design avoids the usual EPD problems such as bubbles and acidic/alkaline microenvironments in the near‐electrode region in aqueous EPD processes. Ultrathin COF membranes with homogenous structures can be produced within several minutes. Consequently, the prepared COF membranes exhibit outstanding permselectivity and possess good stability and anti‐pressure ability due to their uniform architecture and unique chemical composition.

Electrochemical Interfacial Polymerization toward Ultrathin COF Membranes for Brine Desalination

“…In recent years, various materials like graphene oxide (GO), metal–organic frameworks (MOFs), conjugated microporous polymers (CMPs), have been successfully fabricated into separation membranes on specific substrates by electrochemical synthesis, exhibiting high fabrication efficiency and separation performance [10] . Very recently, a top‐down based electrophoretic deposition has been developed, demonstrating a physical method to fabricate pre‐synthesized ionic COF nanosheets into stacked ionic COF membranes [11] . However, due to the lack of sufficient designability of the COF reaction route, it remains a grand challenge to incorporate electrochemical reaction in preparing ultrathin COF membranes and regulating interfacial polymerization process of COF membranes [12] …”

“…[10] Very recently, a top-down based electrophoretic deposition has been developed, demonstrating a physical method to fabricate pre-synthesized ionic COF nanosheets into stacked ionic COF membranes. [11] However, due to the lack of sufficient designability of the COF reaction route, it remains a grand challenge to incorporate electrochemical reaction in preparing ultrathin COF membranes and regulating interfacial polymerization process of COF membranes. [12] In this study, we develop the electrochemical interfacial polymerization for preparing ultrathin COF membranes.…”

Emerging Covalent Organic Frameworks for Efficient Proton Conductors

“…The preparation of COF membranes has made significant progress over the past years. The primary methods for preparing COF membranes that have been reported include solvothermal synthesis, ,− interfacial polymerization, − layer-by-layer assembly, ,− solution casting, , and solid-state synthesis. ,, Different methods, however, result in different membranes and hence different application scenarios. In this section, we will introduce proton-conducting COF membranes fabricated by different methods.…”

Colloidal 2D Covalent Organic Framework-Tailored Nanofiltration Membranes for Precise Molecular Sieving

“…The contamination of water sources poses a significant threat to human survival, with wastewater from textile factories accounting for one-fifth of the commercial water scarcity issues. − Due to the complexity of contaminant compositions and the potential danger to organisms, the efficient treatment of textile wastewater is crucial. − Nanofiltration (NF) is a pressure-driven membrane filtration process, and the pore size of the NF membrane is 1–2 nm. The pore size of NF membranes matches well with the molecular size of dyes, and thus, NF membranes have received great attention in the field of textile wastewater treatment. , Recently, advanced NF membranes with sharp molecular weight cut-offs (MWCO) show great advantages in precise molecular sieving, which can enable complex molecular separation for sustainable molecular recovery and purification from textile wastewater or high value-added reutilization. − …”