Controllable and Rapid Synthesis of Conjugated Microporous Polymer Membranes via Interfacial Polymerization for Ultrafast Molecular Separation

Conjugated microporous polymers (CMPs) featuring a well-structured microporosity are desirable molecular sieving materials, but most are fabricated under harsh synthesis conditions (e.g., high temperature and pressure) and are insoluble, which is challenging for processing them into continuous membranes. Herein, in situ formation of imine-linked, 31-nm-thick CMP nanofilms supported on porous polymeric substrates via catalysis diffusion-controlled interfacial polymerization (IP) under mild conditions is reported. The diffusion of catalyst acetic acid (AcOH) from the water phase to the interface enables acceleration of the aldehyde-amine condensation from the oil phase and thus the formation of CMP nanofilms within 10 min. The micropore size and thickness of CMP membranes were feasibly regulated by rational utilization of molecular ligands and control of IP parameters. Importantly, introducing hydroxyl groups adjacent to aldehyde enlarges CMP pore apertures from 1.0 to 1.7 nm due to the reduced reactivity induced by steric hindrance and the formed intramolecular hydrogen bonds. The newly synthesized 2,5-dihydroxyterephthaldeyde–m-phenylenediamine membranes display an extraordinarily high water permeance (240.0 L m–2 h–1 bar–1) and an excellent brilliant blue R (825.9 Da) rejection (i.e., 98.3%). In addition, the CMP membranes achieve an unprecedented sieving capability for both dye/dye and dye/divalent salt mixtures. This catalysis diffusion-controlled, interface-confined polymerization means may enable the development of new coherent microporous organic polymer films with potential for water purification, adsorption, and gas purification.