Nanopore breathing molecule separation gets theoretical explanation
A Nature Communications study says timed nanopore fluctuations can help separate molecules with small mass differences, such as H₂O and D₂O.
By Lucas Ferreira · Science & Environment Writer
3 min read
A July study in Nature Communications gives a theoretical basis for nanopore breathing molecule separation, a process that could improve how porous materials sort molecules that are nearly alike. The work matters because separation technologies are widely used in chemical and biochemical applications, where small molecular differences can be difficult to exploit.
The study was led by Professor Shinji Saito of the Institute for Molecular Science in Japan, according to Kyoto University. The researchers used ordinary water, H₂O, and heavy water, D₂O, as a test case for how molecules move through nanopores in a metal-organic framework.
Kyoto University said the new work builds on earlier research by Professor Susumu Kitagawa of Kyoto University’s Institute for Integrated Cell-Material Sciences and colleagues. That earlier study, published in Nature, showed that nanoporous materials could separate H₂O from D₂O, two forms of water with similar overall properties but different masses.
What is nanopore breathing in molecule separation?
Nanopore breathing refers to small structural fluctuations in porous materials as their openings shift over time and in response to passing molecules. In molecule separation, those motions can affect which molecules move through the pore more easily.
Metal-organic frameworks are porous materials made from metal nodes linked by organic components, according to Kyoto University. Because they contain many tiny openings, they can be used to separate molecules in several settings, but their performance depends on both the pore structure and the molecules being separated.
Traditional explanations often focus on pore size and molecular shape. Saito’s team examined a more dynamic question: how changes in the energy barrier inside a nanopore influence diffusion and selectivity.
Using quantum chemical calculations designed to represent soft porous crystals such as metal-organic frameworks, the researchers modeled how nanopore fluctuations affect transport. Kyoto University said the team found that structural fluctuations were the leading factor controlling how molecules moved and separated in the framework.
The calculations also pointed to an optimal fluctuation rate. At that rate, diffusion through the nanopore framework reached its highest efficiency, according to the study summary.
The H₂O and D₂O comparison showed why mass matters. Although the two molecules differ only slightly in mass, the researchers found that the difference produced clear changes in diffusion through the nanoporous material.
Saito said, according to Kyoto University, that the best fluctuation rate depends on molecular mass. That means a material’s own dynamics could be tuned to speed one molecular species more than another, creating transport selectivity.
The finding suggests a design route for future separation materials. Rather than treating pores as fixed openings, researchers could use controlled motion within the material to improve separation performance.
Saito said the concept could apply beyond the water example and may help design smarter separation materials. Kyoto University said such materials could reduce energy use and improve industrial separation technologies.
The paper, “Fluctuation-driven mass-selective transport in dynamic nanopores,” was authored by Zhiye Tang and colleagues and published in Nature Communications. Its DOI is 10.1038/s41467-026-75540-5.
This story draws on original reporting from Phys.org.