Polyamide nanofilms with linearly-tunable thickness for high performance nanofiltration

Polyamide composite membranes synthesized by conventional interfacial polymerization (IP) have attracted much attention for desalination to overcome the water shortage crisis. A big challenge is remained to desirably tune the thickness of polyamide nanofilms in these composite membranes by the uncontrollable IP process. Herein, we report a rational strategy to linearly regulate the nanofilm thickness from 32.3 to 5.6 nm by using glycerol as a water soluble and environment friendly additive to make the IP process controllable. The synthesized nanofilms display tuneable cross-linking degree and pore size, endowing the polyamide membranes with desirable water permeability and salt selectivity. Our membranes exhibit a rise of 51% in water permeance and keep the rejection ratio to Na2SO4 above 99.4% when the nanofilm thickness decreases from 32.3 to 15.1 nm. This strategy opens an eco-friendly and scalable avenue for synthesizing polyamide nanofilms which are deeply needed for nanofiltration, reverse osmosis and forward osmosis.