Ligand-engineered layered solid-liquid interfaces enable fast and selective ion transport

Fast and selective ion transport is essential to electrochemical energy storage, ion separation, micro- and nanofluidics, and interfacial catalysis. In nonaqueous media, however, weak dielectric screening promotes ion pairs and clusters, tightly coupling salt dissociation, solvent reorganization and ion migration. Increasing mobility can therefore accelerate both cations and anions, while overly strong interfacial binding can create traps that slow the target ion.

 

A team of material scientists led by Jianwei Nai from Zhejiang University of Technology in Hangzhou, China recently developed a ligand-engineered solid-liquid interface that addresses this rate-selectivity trade-off. The researchers combined a layered cyano-bridged metal framework, or CMF, with four representative solvents: N,N-dimethylformamide, dimethyl sulfoxide, pyrazine and pyridine.

 

The study was published online in Nano Research on June 15, 2026.

 

Molecular dynamics simulations showed that the CMF interface increased room-temperature lithium-ion conductivity by roughly 1.5 to 10 times compared with the corresponding bulk liquids, reaching 9.5 mS cm^-1. The simulated lithium-ion transport selectivity rose from about 0.35-0.50 in bulk liquids to nearly 0.9. The interface did not simply accelerate every ion. Instead, it created connected lithium-rich, low-free-energy regions near the layered surface while enriching and retaining FSI^- anions at framework sites, weakening short-range lithium-anion association and suppressing anion co-migration.

 

The team then tested whether the mechanism depended on an ideal, macroscopically aligned surface. Multi-patch models containing discontinuous, randomly oriented CMF domains still outperformed bulk-liquid controls. Experiments on CMF-containing quasi-solid electrolyte pellets showed the same trend: ionic conductivity increased from 0.15-0.75 to 0.40-0.85 mS cm^-1, and the lithium-ion transference number increased from 0.27-0.45 to 0.49-0.54. Defect models further indicated that the interface tolerates moderate loss of accessible metal sites, although high performance requires sufficient site density and surface continuity.

 

“Rather than treating the solvent as an inert background, this work assigns solvent molecules distinct interfacial functions,” said Jianwei Nai, a corresponding author of the study. “The solid framework and the surrounding liquid cooperate to reorganize lithium-ion pathways and salt speciation.”

 

The researchers identified two complementary ligand roles. Outer-layer solvent ligands can coordinate with both lithium ions and undercoordinated M₁ metal sites. Competition between these interactions perturbs the lithium solvation shell and promotes ligand exchange. Nitrogen-donor ligands such as pyrazine and pyridine showed shorter lithium-solvent residence times, about 33 ps, and faster solvation renewal, which correlated with higher lithium-ion conductivity. Outer-layer ligands therefore mainly controlled transport rate.

 

Interlayer solvent ligands instead controlled the morphology of the CMF layers. Oxygen-donor ligands tended to produce curved surfaces, whereas nitrogen-donor ligands stabilized nearly planar, low-curvature structures. Flatter layers improved access to M₂ sites that anchor FSI^- anions, reduced lithium-anion association and maintained more continuous migration regions. Interlayer ligands consequently had a strong effect on transport selectivity and also contributed to the overall rate.

 

To convert these mechanisms into a selection rule, the team introduced the polarity symmetry of solvent ligands, or PSSL, which describes the spatial uniformity of a molecule’s electrostatic distribution. PSSL correlated with solvation-renewal rate for outer-layer ligands and with surface curvature for interlayer ligands. Mapping the descriptor onto a two-dimensional rate-selectivity space linked an intrinsic molecular property to interfacial structure and macroscopic transport performance.

 

“The next step is to expand the ligand and salt library and determine how broadly the PSSL rule applies across different ions and solid-liquid interfaces,” Nai said. “The long-term goal is to move interfacial solvent selection from trial and error toward predictive molecular design.”

 

The strategy may inform selective ion-conducting electrolytes, separation membranes, micro- and nanofluidic devices, and other nonaqueous systems that require rapid transport without sacrificing selectivity.

 

Other contributors include Qiangqiang Qiao, Shaowei Li and Bing Liu contributed equally to the study. Other authors are Shuai Li, Shihui Zou, Peng Shi, Yujing Liu, Huadong Yuan, Jianmin Luo, Yao Wang and Xinyong Tao, all affiliated with Zhejiang University of Technology through the participating colleges and institutes.

 

This work is supported by the National Natural Science Foundation of China (Nos. 52521010, 52473282, 52225208), the Natural Science Foundation of Zhejiang Province (Nos. LZ23E020002, LZYQ25E020002), and the Fundamental Research Funds for the Provincial Universities of Zhejiang (Nos. RF-C2023002, RF-A2023001).

 

 

DOI Link:

https://doi.org/10.26599/NR.2026.94908934

 

About Nano Research

Nano Research is a peer-reviewed, open access, international and interdisciplinary research journal, sponsored by Tsinghua University and the Chinese Chemical Society, published by Tsinghua University Press on the platform SciOpen. It publishes original high-quality research and significant review articles on all aspects of nanoscience and nanotechnology, ranging from basic aspects of the science of nanoscale materials to practical applications of such materials. After 18 years of development, it has become one of the most influential academic journals in the nano field. Nano Research has published more than 1,000 papers every year from 2022, with its cumulative count surpassing 8,000 articles. In 2025 InCites Journal Citation Reports, its 2025 IF is 9.4 (8.3, 5 years), and it continues to be the Q1 area among the four subject classifications. Nano Research Award, established by Nano Research together with TUP and Springer Nature in 2013, and Nano Research Young Innovators (NR45) Awards, established by Nano Research in 2018, have become international academic awards with global influence.

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