Separation Performance of Membranes Containing Ultrathin Surface Coating of Metal-Polyphenol Network

Metal–polyphenol networks (MPNs) are being used as versatile coatings for regulating membrane surface chemistry and for the formation of thin separation layers. The intrinsic nature of plant polyphenols and their coordination with transition metal ions provide a green synthesis procedure of thin films, which enhance membrane hydrophilicity and fouling resistance. MPNs have been used to fabricate tailorable coating layers for high-performance membranes desirable for a wide range of applications. Here, we present the recent progress of the use of MPNs in membrane materials and processes with a special focus on the important roles of tannic acid–metal ion (TA-Mn+) coordination for thin film formation. This review introduces the most recent advances in the fabrication techniques and the application areas of TA-Mn+ containing membranes. In addition, this paper outlines the latest research progress of the TA–metal ion containing membranes and summarizes the role of MPNs in membrane performance. The impact of fabrication parameters, as well as the stability of the synthesized films, is discussed. Finally, the remaining challenges that the field still faces and potential future opportunities are illustrated.