Surface-Tension-Governed Nanoconfinement for Tunable Hydrogen-Isotope Transport

Interfacial forces and nanoconfined environments play crucial roles in transport phenomena within low-dimensional materials. In this study, we propose a photothermally regulated surface-tension mechanism for hydrogen-isotope fractionation, in which light-induced changes in the surface tension of gallium ( Ga ) dynamically modulate the confined environment between graphene oxide ( GO ) layers. Under near-infrared irradiation, the surface tension of Ga decreases, altering its wettability within the interlayer galleries and inducing a reversible contraction of the GO interlayer spacing. temperature-dependent transmission electron microscopy confirmed this dynamic modulation, showing that confined Ga nanoparticles undergo fully reversible expansion-contraction and display surface-energy-driven extension behavior analogous to macroscopic particles. Such confinement-induced structural responsiveness regulates the local arrangement of water molecules, leading to distinct molecular aggregation states for H 2 O and D 2 O . Due to stronger intermolecular attraction, D 2 O diffusion is more restricted in confinement, leading to pronounced isotope selectivity. Experimentally, the membrane achieved a separation factor of 70.53 for H 2 O : D 2 O and demonstrated selective removal of tritium water ( T 2 O ). Our study elucidates the interplay between photothermally driven interfacial energy modulation and confined molecular transport, offering new insights into tunable separation processes and interfacial physics.