Helium Isotopes Quantum Sieving Through Graphtriyne Membranes

TL;DR

This study uses quantum calculations to analyze helium isotope separation through graphtriyne membranes, revealing significant quantum effects and isotope selectivity at low temperatures, challenging previous assumptions about pore size limitations.

Contribution

It provides the first detailed quantum analysis of helium isotope sieving in graphtriyne membranes, highlighting the importance of quantum effects and resonance phenomena.

Findings

Quantum effects dominate helium isotope permeation at low temperatures.

Heavier helium isotopes can cross more efficiently than lighter ones under certain conditions.

Approximate methods like transition state theory may lead to significant errors in this context.

Abstract

We report accurate quantum calculations of the sieving of Helium atoms by two-dimensional (2D) graphtriyne layers with a new interaction potential. Thermal rate constants and permeances in an ample temperature range are computed and compared for both Helium isotopes. With a pore larger than graphdiyne, the most common member of the gamma - graphyne family, it could be expected that the appearance of quantum effects were more limited. We find, however, a strong quantum behavior that can be attributed to the presence of selective adsorption resonances, with a pronounced effect in the low temperature regime. This effect leads to the appearance of some selectivity at very low temperatures and the possibility for the heavier isotope to cross the membrane more efficiently than the lighter, contrarily to what happened with graphdiyne membranes, where the sieving at low energy is predominantly ruled by quantum tunneling. The use of more approximate methods could be not advisable in these situations and prototypical transition state theory (TST) treatments might lead to large errors.