Rigid cross-linking: A structural stabilization strategy for enhancing the swelling and compression resistance of GO-based membranes

Graphene oxide membranes (GOMs) are a focal point in nanofiltration research due to their exceptional stability and tunable nanometer-scale interlayer structures. However, the weak interactions (e.g., π–π stacking, hydrogen bonding) maintaining GO interlayers are prone to instability, leading to swelling or compression under external stimuli and posing challenges for precise molecular sieving. To address this, the authors propose intercalating PPy-encapsulated UiO-66-NH₂ (PPy@UiO) as a rigid crosslinker within GOMs. The amino groups on PPy@UiO bind adjacent GO layers via electrostatic interactions, suppressing swelling, while the rigid and porous structure enhances mechanical stability without compromising permeability. The GO/PPy@UiO composite membrane exhibits minimal swelling, with interlayer spacing increasing by only 1 Å in hydrated conditions (10.06 Å vs. 9.05 Å dry), significantly less than the 4.7 Å observed in pure GOM. Moreover, the membrane maintains consistent dye rejection performance under both low (1 bar) and high (5 bar) pressures, achieving 71.3 % rejection for methylene blue (MB) and 96.3 % for Evans blue (EBT). Crucially, this structure demonstrates long-term stability over 60 h and allows precise tuning of interlayer spacing and filtration performance by adjusting UiO particle growth. This work provides a practical strategy for designing high-performance, stable, and tunable nanofiltration membranes.