Constructing piperazine-integrated covalent organic framework nanofiltration membranes with enhanced antifouling properties for efficient and selective molecular separation

Abstract

With the increasing demand for industrial wastewater treatment, nanofiltration (NF) membranes face technical bottlenecks in selectivity and permeance when separating dyes and inorganic salts. To address this challenge, high-performance NF membranes based on covalent organic framework (COF) were designed and successfully prepared in this study. The COF composite membrane (COF-CM) was constructed using interfacial polymerization method, and exhibited excellent separation performance. The membrane exhibited a pure water permeance of 100.6 L/(m² h bar) and a rejection efficiency of over 98.0% for congo red (CR), with a rejection efficiency for Na₂SO₄ and NaCl of only 10.72% and 1.47%, respectively, indicating outstanding selectivity. Further modification of the membrane structure with piperazine yielded PIP-COF-CM, which maintained high dye rejection (CR > 97%) and significantly enhanced antifouling performance, achieving a permeance recovery ratio exceeding 96.0%. The composite membrane demonstrated stable separation efficiency for dye/salt systems, exhibiting excellent performance over 72 h of continuous operation. This work offers an innovative membrane material solution for the efficient and sustainable treatment of industrial wastewater, particularly in challenging dye/salt separation systems.