Mass transport within zeolites is pivotal in determining the accessibility of active sites to reactants and hence the catalytic performance. However, there lacks of quantitative guidance for synthesis of desired zeolites with reduced diffusion limitation. Herein, we take mordenite (MOR) zeolite as a model, which is characterized by 12-membered rings (MR) channels as transport path towards the active sites within the 8MR side pockets for syngas conversion to light olefins. By correlating the effective diffusion lengths (