Thermochemically Engineered Cellulose-Directed Development of Pyrolyzed Cu–BTC Free-Standing Membranes for Sustainable Forward Osmosis of Real Industrial Effluents

Abstract

The development of energy-efficient and structurally robust forward osmosis (FO) free-standing membranes is essential for treating chemically real industrial wastewaters while promoting sustainable resource utilization. Herein, an integrated materials strategy involves biomass valorization with metal-organic framework (MOF)-derived functional engineering to construct a high-performance free-standing FO membrane. Cellulose extracted from areca husk, an abundant agricultural residue, was incorporated during Cu–benzene-1,3,5-tricarboxylate (Cu–BTC) synthesis to regulate nucleation and enhance interfacial chemistry. Subsequent pyrolysis at 900 °C converted the hybrid framework into a porous carbon–copper (P–Cu–BTC) enriched with oxygen-functional groups and stabilized metallic domains, thereby improving structural integrity, surface polarity, and transport pathways. Comprehensive physicochemical characterization confirmed phase transformation, chemical evolution, enhanced porosity, and improved thermal stability. The optimized 1% P–Cu–BTC membrane was integrated into a poly(ether sulfone) (PES) matrix to fabricate a free-standing FO membrane. Using recyclable EDTA-2Na as a draw solution, the optimized membrane demonstrated an osmotic water flux (OWF) of 5.20 ± 0.1 L m^–2 h^–1, a controlled reverse solute flux (RSF) of (1.22 ± 0.10) × 10^–7 mol·m^–2·h^–1, and a low specific solute concentration (SSC) of (2.34 ± 0.00) × 10^–8 mol L^–1, compared to a commercial reverse osmosis (RO) membrane, and achieved high rejection of organic dyes and stable treatment of industrial pharmaceutical, distillery, and sugar effluents with high OWF and controlled reverse solute flux (RSF). Further, long-term performance over 120 h without washing confirms strong antifouling resistance and structural durability, without reducing performance. This work establishes a scalable MOF-derived free-standing membrane platform for energy-efficient industrial wastewater treatment and sustainable water reclamation under real-world challenges.