Ultranarrow nanochannels in a staggered two-dimensional polymer membrane enhance electric double-layer coverage for osmotic energy harvesting
In a recent article published in Nature Communications, researchers from the Max Planck Institute of Microstructure Physics and TU Dresden reported an ultrathin staggered viologen-incorporated two-dimensional polymer membrane for efficient osmotic energy harvesting. By engineering ABC interlayer stacking, the membrane forms ultranarrow triangular nanochannels with enhanced electric double-layer coverage, enabling highly selective anion transport and high-power output under salinity gradients.
Two-dimensional framework membranes (2DFMs) are promising materials for osmotic energy harvesting because their ordered nanochannels and charged surfaces can regulate ion transport under salinity gradients. However, many existing 2DFMs contain relatively large channels and/or insufficient charge density, resulting in limited electric double-layer coverage and reduced ion selectivity.
A recent article by researchers from the Max Planck Institute of Microstructure Physics, TU Dresden, and collaborating institutions, published in Nature Communications, reports an ultrathin staggered viologen-incorporated 2D polymer membrane, termed sV2DP, for high-performance osmotic energy harvesting. Through ABC interlayer-stacking engineering, the membrane forms vertically aligned ultranarrow triangular nanochannels with an effective diameter of 1.36 nm and densely distributed positively charged pyridinium sites. This structural design substantially enhances the electric double-layer (EDL) coverage within the nanochannels. Compared with its non-staggered analogue, the sV2DP membrane shows a 3.2-fold enhancement in EDL coverage under a 50-fold KCl gradient. As a result, the membrane combines high anion selectivity with efficient ion conduction, achieving an inferred chloride transference number of 0.85 and a selective current density of 14.6 kA m-2. Molecular dynamics simulations further reveal that the spirally arranged charged sites in the ABC-stacked channels guide chloride ions along a characteristic “screw-like” migration pathway, promoting efficient transmembrane anion transport.
When integrated into micro-aperture osmotic power generators, the sV2DP membrane delivered a peak power density of 243 W m-2 under a 50-fold NaCl gradient, placing it among the highest-performing 2DFM systems reported under comparable conditions. The membrane also exhibited high mechanical robustness, with a Young’s modulus of 37.5 ± 1.2 GPa, enabling its integration into aperture-array devices. In a 45 × 45 aperture-array osmotic power generator, the membrane maintained stable power generation over nine days under artificial seawater/river water conditions, demonstrating its potential for scaled-area operation and long-term durability.
The paper entitled “Ultranarrow nanochannels in a staggered two-dimensional polymer membrane enhance electric double-layer coverage for osmotic energy harvesting” by Feng Ni, Ye Yang, Shuangjie Zhao, Mahabir Prasad, Naveen Goyal, Xusheng Yang, Dongxu Wang, Jianjun Zhang, Mike Hambsch, Miroslav Polozij, Stefan C. B. Mannsfeld, Ute Kaiser, Grégory F. Schneider, Thomas D. Kühne, Thomas Heine, Zhiyong Wang, and Xinliang Feng can be found at: https://www.nature.com/articles/s41467-026-74696-4, DOI: 10.1038/s41467-026-74696-4
