Novel methodologies and materials for facile fabrication of nanofiltration membranes

Nanofiltration, as innovative membrane technology, has been applied for various interesting separation applications including wastewater treatment and molecular separation including salts, dyes, and other small organic molecules. In recent years, several molecularly designed framework systems such as metal–organic framework (MOFs), covalent organic framework (COF), two-dimensional (2D) materials such as MXene, typical natural polyphenols like tannic acid, dopamine, and carbon nanomaterials like graphene oxide (GO) have been employed in the fabrication process of nanofiltration membranes for developing the presentation and overcome the drawbacks of conventional ones. COFs and MOFs as crystalline porous materials with distinct superiorities including high surface areas, structure tolerability, versatile topology architectures, and well-defined nanometer pores, as well as readily customizable functionalities, are promising candidates to prepare next-generation membranes. Also, 2D MXene material has potential in building membranes and molecular separation owing to high conductivity, excellent physicochemical performance, hydrophilic surface, and advanced stability. On the other side, tannic acid has excellent chemical activity due to phenolic hydroxyl groups in the structure, so, it has been extensively used for water-phase monomer in an interfacial polymerization process. Furthermore, GO with 2D construction, outstanding chemical stability, and anti-fouling features have been applied for the functionalization of the NF membrane. Moreover, bioinspired polydopamine with strong adhesion to metal ions, and increased hydrophilicity, is a good candidate for nanofiltration membranes. Since the interest and attention in this field are increasing, here, a review is conducted for summarizing the latest fabrication techniques for membranes based on tannic acid, COF, MOF, MXene, graphene oxide, and dopamine and their uses in terms of water treatment.