Sub-5 nm polyamide nanofilms combined with transfer-printing compositing for ultrafast nanofiltration

Abstract

Synthesizing ultrathin polyamide nanofilms via interfacial polymerization (IP) at free interface offers a promising route to achieving preferential separation performance. However, one of big challenges lies in how to acquire large-scale synthesis and defect-free transfer of sub-5 nm polyamide nanofilms into robust composite membranes. Herein, we report an integrated strategy to allow for scalable synthesis and seamless compositing of sub-5 nm polyamide nanofilms that exhibit ultrafast and robust nanofiltration performance, by virtue of glycerol-regulated IP at free interface and transfer-printing compositing. Distinct from conventional hexane-water interface, our method leverages hexane-water/glycerol interface to boost interface stability of IP and confine monomer diffusion, enabling controllable synthesis of large-scale, defect-free sub-5 nm polyamide nanofilm. Meanwhile, a facile and universal transfer printing method is employed to integrate nanofilms on various substrates with high interfacial strength, which is not achievable with conventional transfer methods. The sub-5 nm polyamide composite membrane exhibits extraordinary water permeance (53.2 L⋅m−2⋅h−1·bar−1) and salt rejection (RNa2SO4 = 97.3%) under ultralow pressure of 1 bar, as well as superhigh water/salt permselectivity surpassing most of the polyamide composite membranes reported. The easy composite method and extraordinary performance in this work make ultrathin polyamide nanofilms a step closer to practical separation scenarios.