Zwitterion-MOF Functional Interface Enabling Robust Ion and Dye Rejection in Water Filtration

Abstract

The effective removal of toxic heavy metals and synthetic dyes from wastewater remains a critical challenge in environmental remediation. In this study, we present a hierarchically engineered nanocomposite membrane that integrates zeolitic imidazolate framework-8 (ZIF-8) and sulfobetaine methacrylate (SBMA) into a polyacrylonitrile-polyvinylpyrrolidone (PAN-PVP) matrix. The membrane exhibits a high pure water flux of 71.96 L·m-2·h-1 and strong rejection efficiencies for cadmium (95.6%), copper (93.3%), and lead (97.8%) ions as well as methyl orange (98.9%) and methylene blue (98.4%) across different pH conditions. Importantly, the membrane retained ∼93% of its performance after 10 continuous cycles, underscoring its durability. A combination of Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and zeta potential measurements confirmed the successful integration and chemical stability of ZIF-8 and SBMA within the membrane. In addition, density functional theory (DFT) and classical all-atom molecular dynamics (MD) simulations were employed to gain molecular-level insights into structural features and intermolecular interactions between contaminants and the ZIF-8/SBMA membrane system. This work introduces a tunable and scalable membrane platform with high flux, selectivity, and robustness, offering both mechanistic insights and practical applications for advanced water purification technologies targeting a wide range of contaminants.