Graphene oxide membranes using MOF@Chitosan core-shell nanoparticles as dual modulators for dye separation

Graphene oxide (GO) membranes hold significant promise for the water purification. However, they also face the problem of structural swelling, which limits their use in water treatment applications. In this work, a novel dual-modulated core-shell metal-organic framework@Chitosan (MOF@CS) was successfully synthesized and used as an intercalation cross-linker to optimize the interlayer spacing and stability of GO membranes. Molecular dynamics simulation confirms that MOF@CS, acting as an intercalator, accelerates the water diffusion rate within the channels of the GO layer compared to a pure GO layer. At the same time, Fourier Transform Infrared Spectroscopy analysis reveals that MOF@CS serves as a cross-linker for covalently cross-linking the GO layer. The nanofiltration performance and stability of the improved MOF@CS-GO composite membranes were significantly enhanced. Compared to the pure GO membranes, the MOF@CS-GO composite membranes exhibited enhanced Congo red rejection rates (from 76.5% to 95.6%) while maintaining a high pure water flux (34.5 L·m-2·h-1·bar-1) and good structural stability (stable dye removal performance over 120 h). This dual regulation strategy is expected to effectively solve the swelling problem of GO membranes in aqueous media and open up avenues for advancing their performance.