Interfacial synthesis of large-area ultrathin polyimine nanofilms as molecular separation membrane
Karishma Tiwari, Solagna Modak, Pulak Sarkar, Santanu Ray, Vasista Adupa, K. Anki Reddy, Sumit Kumar Pramanik, Amitava Das, Santanu Karan
Abstract
Thin film membranes of covalent organic frameworks are promising for high-permeance molecular separation. However, their synthesis needs a high temperature or longer reaction time, unsuitable for large-scale fabrication of thin film composite membranes. The ultrathin film of porous organic polymers as a separation layer of the composite membrane could be a close alternative to COF membranes. Here we report transition metal ion-catalyzed room temperature fabrication of the ultrathin (≈12 nm) polyimine nanofilms via interfacial polymerization of melamine and triformylphloroglucinol onto hydrolyzed polyacrylonitrile support within a short reaction time. Composite membranes exhibit high water permeance (≈78 L m−2 h−1 bar−1), high rejection (99.6%) of brilliant blue R (825.9 g mol−1), low rejection of NaCl (≈1.8%) and Na2SO4 (≈17%), and enable efficient molecular separation. The role of metal ion catalysts for large-area fabrication of the ultrathin polyimine nanofilm membranes used for molecular separation is demonstrated.