Interfacial Engineering of Sulfonated Polyethersulfone/ZIF‐8 Forward Osmosis Membranes: Applying Sulfonation and Interlayers for Enhanced Desalination Performance

ABSTRACT This study explores the strategic synthesis of sulfonated polyethersulfone (SPES) with tunable sulfonation degrees to engineer selective interfacial layers (SLs) for thin‐film composite (TFC) forward osmosis (FO) membranes. To overcome the persistent trade‐off between water permeability and salt rejection in conventional TFC membranes, this work introduces an interlayer engineering strategy utilizing zeolitic imidazolate framework‐8 nanoparticles (ZIF‐8 NPs). Unlike traditional approaches that focus solely on membrane surface modification, the integration of ZIF‐8 as a nanostructured interlayer addresses interfacial defects and enhances solute screening by leveraging its molecular sieving capabilities and hydrophilicity through the Janus membrane effect. SPES‐based membranes exhibited a notable enhancement for water flux from 15.23 to 32.12 L/m 2 h compared to neat polyethersulfone (PES) SLs. Simultaneously, the salt rejection effectively reached 93.9% for SPES/ZIF‐8/PA(#2). XRD and FTIR analyses confirmed the crystallinity and chemical integrity of ZIF‐8 NPs, while FESEM revealed their uniform dispersion across the SL surface. Notably, the sulfonation process not only enhanced surface porosity but also created a chemically reactive interface for ZIF‐8 anchoring, a dual‐functionality rarely achieved in prior studies. The findings offer a scalable framework for designing high‐performance TFC membranes with hierarchically engineered interfaces, paving the way for next‐generation desalination and resource recovery systems.