Oxygen plasma-assisted contra-diffusion self-assembly of covalent organic framework pervaporation membranes for organic-solvent dehydration

Abstract

Pervaporation is considered to have great potential for application in the field of organic-solvent dehydration. In this study, a type of keto-enamine-linked covalent organic framework TpPa (synthesized using the Schiff-base reaction of 1,3,5-triformylphloroglucinol [Tp] with p-phenylenediamine [Pa]), was fabricated on commercial polyacrylonitrile (PAN) ultrafiltration membranes through an oxygen-plasma assisted contra-diffusion self-assembly strategy for organic-solvent dehydration. The PAN membranes with a glycerol exhibited a better separation factor for dehydration of organic solvents than those without a glycerol layer. The influence of oxygen plasma and glycerol on the formation of the TpPa membrane was investigated. The best plasma treatment condition and optimum glycerol impregnation concentration were determined as a device power of 60 W and 30 wt%, respectively. Defect-free TpPa membrane formation took only 24 h. The as-prepared TpPa membrane exhibited a separation factor of 1491 and a high permeation flux of 2530 g m−2 h−1 for a 90 wt% isopropanol–water mixture. The separation performance of the TpPa membrane was stable for >100 h, exhibiting great potential in organic-solvent dehydration.