TST-based calculation of gas flux through a zero-dimensional pore is promising for predicting the gas separation performance for NATM. It helps one bypass the lengthy MD simulations, especially when molecular transport is a rare event, e.g., for O2 in the current study. While TST calculations have been used in the past to estimate transport rates, the propagation for error is high mainly because of assumptions made for the estimation of energy barrier and pre-exponential coefficient.