Tunnel Effect of ZIF-8 Incorporated in a Polysulfone Matrix

Traditional polysulfone (PSF) membranes are constrained by inherently low permeability and insufficient antifouling capability. Incorporating zeolitic imidazolate framework-8 (ZIF-8), a material characterized by its highly porous architecture and large specific surface area, offers an effective strategy for improving membrane porosity and introducing additional adsorption-active sites. In this work, two different-sized ZIF-8 particles (Z₁: ∼50 nm, Z₂: ∼250 nm) were employed to elucidate how ZIF-8 functions as an auxiliary water transport pathway within PSF/ZIF-8 composite membranes. Electrochemical impedance spectroscopy (EIS) analyses showed that membrane effective ionic pathway connectivity increased progressively with higher ZIF-8 loadings, and the composite membrane containing Z₁ exhibited a notably higher porosity than that incorporating Z₂. The incorporation of ZIF-8 significantly enhanced the water permeability of PSF membranes, and a pronounced negative correlation was observed between the electrochemical impedance values and water flux. Furthermore, in situ EIS measurements demonstrated that the composite membranes incorporating ZIF-8 particles exhibited excellent antifouling performance, indicating that EIS can serve as a cost-effective and real-time monitoring tool for assessing membrane separation performance.