We now discuss how the observed changes affect the CO 2 capture performance rank-order. Potentially interesting materials, with high productivity and low energy cost, may lose their high ranking upon consideration of microscopic diffusivity. Figure depicts this effect whereby low diffusivity materials drop from the upper ranks upon increasing importance of microscopic diffusivity in the overall mass-transfer coefficient. Materials with higher diffusion coefficients are shown with nearly horizontal curves, as the increase in R µ does not severely affect K eff and hence process based performance. On the other hand, lower diffusivity materials are characterised by drops (rises) in productivity (energy cost) upon increasing R µ . These results are in accordance with the behaviour of K eff in Figure .