High temperature resistant thin film composite polyamide membrane constructed via 3,3′-diamine-Tröger base COFs for enhancing reverse osmosis separation performances

High temperature resistant thin-film composite polyamide (TFC PA) membranes are notable across various applications. However, the pursuit of efficient separation at elevated temperatures was hindered by the thick and unstable active layer. In this work, based on covalent organic frameworks (COFs) decorated with exceptional porosity, remarkably large specific surface areas, and outstanding thermal stability, a TFC PA reverse osmosis (RO) membrane featuring a slimmer selective layer and enhanced thermal stability was achieved through interfacial polymerization mediated by COF nanoparticles as aqueous-phase modifier. Firstly, a novel COF TpDATB nanoparticles with high free volume and rigidity were designed and synthesized based on 3,3'-diamine-Trögers base (DATB) with V-shaped rigid structure and 1,3,5-Triformylphloroglucinol (Tp). The introduction of COF TpDATB nanoparticles retards the penetration of the aqueous phase into the organic phase, facilitating the formation of a thinner and more uniform PA selective layer. The resultant COF TpDATB modified TFC RO membrane exhibited a water permeance of 35.8 L/(m 2 ·h) and high salt rejection rate of 99.6%. Notably, the hydrogen bond crosslinking density might be increased owing to hydrogen bond formation between carboxyl groups of PA separation layer and a tertiary amine group of COF TpDATB , which further guarantee the high salt rejection under high temperature. The membrane showed a high water permeance of 83.7 L/(m 2 ·h) and rejection rate of 99.1% even at 70 °C. Overall, enhanced by incorporation of COF TpDATB nanoparticles, TFC PA RO membrane exhibited excellent thermal stability and separation efficiency. The current work is envisaged to supply direction for the high-performance TFC PA RO membrane for high temperature resistance.