Synergetic effects of COFs interlayer regulation and surface modification on thin-film nanocomposite reverse osmosis membrane with high performance

Reverse osmosis (RO) membrane technology is of great significance to solve the increasingly serious fresh water supply problem. Researchers have found that substrate and polyamide layer properties influence the separation performance of RO membranes greatly. In this work, an interlayer of ultra-thin and hydrophilic two-dimensional Covalent organic frameworks (COFs) nanomaterial was in-situ constructed on commercial polysulfone (PSf) substrate surface via interfacial reaction between 1,4-phenylenediamine-2-sulfonic acid (Pa-SO3H) and 1,3,5-triformylphloroglucinol (Tp), both with ultra-low concentration. This COFs interlayer successfully adjusted the interfacial polymerization (IP) process between m-phenylenediamine (MPD) and trimesoyl chloride (TMC), and thus helped to fabricate a kind of thin-film nanocomposites (TFN) RO membrane with excellent performance. Compared with the baseline thin-film composite (TFC) RO membrane without COFs interlayer, the water permeance of the TFN RO membrane was increased from 17.0 to 26.3 L m−2 h−1 MPa−1, accompanied with a NaCl rejection remaining about 99.3 %. The TFN RO membrane was further modified by ultra-low concentration Tp aqueous solution to reduce the surface defects and improve the separation performance. The formed TFN-Tp RO membrane has a further increased water permeance from 26.3 to 31.1 L m−2 h−1 MPa−1, and an increased NaCl rejection from 99.3 % to 99.5 % as compared with the TFN RO membrane.