Adjustable structures and anti-fouling covalent organic networks membranes for precise organic small molecules separation

Abstract

Covalent organic networks (CONs) membranes show unprecedented potential for the separation of organic small molecules owing to their adjustable structure and surface properties. Despite the variety of methodologies available for synthesizing CONs membranes, the preparation of CONs membranes by interfacial polymerization (IP) at 25 °C in a shorter period of time remains a great challenge. In this work, a highly anti-fouling EDA-TPA CONs composite nanofiltration (NF) membrane with adjustable structure was constructed by rapid IP of amine (ethylenediamine, EDA) and aldehyde (terephthalaldehyde, TPA) at 25 °C for 3 h. EDA-TPA CONs composite membranes showed good selectivity for most common organic small molecules, achieving a permeance of 35 L h⁻¹ m⁻² bar⁻¹. Moreover, with respect to anti-fouling properties, the EDA-TPA CONs composite membranes exhibited a 96 % flux recovery ratio (FRR) during bovine serum albumin (BSA) filtration, reflecting an 81 % improvement compared to the control membranes (hydrolyzed polyacrylonitrile, HPAN). In addition, the EDA-TPA CONs composite membranes displayed robust comprehensive stability after continuous operation of 480 min, 5 times of cyclic testing, 180 min of continuous ultrasound at 16 kHZ and 24 h of mechanical agitation at 100 rpm. After these extensive evaluations, the EDA-TPA CONs composite membranes still retained their original separation efficacy. This study provides a fast and mild preparation process to fabricate the high performance CONs composite membranes with good anti-fouling performance and stability for treatment of organic small molecules in wastewater.