Sub-nanoconfined selective transport and competitive permeation behaviors in carbon molecular sieve membranes for gas separation

Abstract

Carbon molecular sieve membranes (CMSMs) derived from finely-engineered polymeric precursor are promising for gas separations. However, the microstructure-determined gas transport characteristics and separation mechanism within CMSM systems remain unclear. Herein, we investigate the sub-nanoconfined selective transport and competitive permeation behaviors of precursor-regulated CMSMs for H₂/N₂ separation, using a combination of experimental analyses, modeling, and nonequilibrium molecular dynamics simulations. Results indicate that the faster permeation of small-sized H₂ molecule through CMSMs, compared to N₂ molecule, is attributable to its larger permeable pore volume and higher connectivity of the pore-channels within the bulk membrane. Despite the distinct difference in preferred adsorption locations within CMSMs with different microporous natures, the aggregation of adsorbed N₂ molecules will hinder the transport of H₂ molecules through the membranes, resulting in competitive permeation. The valuable insights into the gas transport behavior and mechanism presented here will benefit the development of next-generation CMSMs for efficient gas separations.