  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.
