Sustainable Fabrication of Cellulose Organic Solvent Nanofiltration Membranes Modified with Metal-Phenolic Networks

While membrane-based separations offer significant energy advantages, conventional fabrication heavily relies on petro-derived polymers and toxic solvents. To address this, we report a highly sustainable route for organic solvent nanofiltration (OSN) membranes using cellulose acetate processed by non-solvent induced phase separation (NIPS) with methyl lactate as a green solvent. Subsequent thermal treatment and alkaline deacetylation yielded robust cellulose membranes with excellent stability in strong solvents, including DMF, NMP, DMSO, and THF. To further optimize performance, a two-step surface modification was employed using tannic acid and multivalent metal salts (Fe³⁺, Al³⁺, Cu²⁺, Zn²⁺) to form stable metal–polyphenol networks. This strategic modification dramatically enhanced polypropylene glycol (PPG) rejection from ~35% to approximately 100% across various organic media, with TA–Fe³⁺ delivering the best performance. Consequently, this approach presents a green, versatile platform for developing solvent-resistant and biodegradable OSN membranes.