Rapid synthesis of charged covalent organic framework for sustainable reverse osmosis membranes

Abstract

Introducing well-structured and selective ionic channels into the polyamide (PA) layer during interfacial polymerization (IP) shows promise for boosting the Donnan and steric exclusion effects, thus enhancing performance. Herein, we propose a novel method to rapidly synthesize water soluble sulfonic acid containing covalent organic framework (SA-COF) nanosheets and incorporated them during IP to precisely adjust ionic groups within the PA layer. The SA-COF's processability and charged nature enhance compatibility with PA, enabling a high loading (10 wt%) without compromising membrane integrity. Additionally, SA-COF integration during IP results in PA membranes with reduced thickness, increased negative charge density, and increased hydrophilicity. Consequently, PA membranes containing 10 wt% SA-COF, denoted as PA-COF₁₀, demonstrated exceptional water permeance (0.98 L·m⁻²·h⁻¹·bar⁻¹), surpassing pristine PA membranes (0.39 L·m⁻²·h⁻¹·bar⁻¹), while maintaining over 98 % rejection for NaCl. Moreover, PA-COF₁₀ membranes exhibited outstanding operational stability and resistance to fouling. This synergistic enhancement of permeance and salt rejection through charged SA-COF integration offers a practical and eco-friendly approach for advanced desalination membrane development, facilitating rapid clean water production.