Work

Carbon molecular sieve membranes derived from UV-irradiated polyimides for enhanced molecular separation and physical aging resistance

Year: 2025

Type: article

Abstract: Herein, we present an approach for adjusting the pore structure of carbon molecular sieve (CMS) membranes by controlling UV irradiation on polyimide (PI) precursors. CMS dense membranes were fabricated by pyrolyzing UV-crosslinkable PIs synthesized from 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA), and 2,4-diamino mesitylene (DAM). Increasing UV irradiation time enhanced molecular sieving performance while decreasing gas permeability. At the highest UV irradiation time of 40 min, the gas selectivities for H 2 /CH 4 and CO 2 /CH 4 improved 3-fold and 2-fold, respectively. Meanwhile, H 2 and CO 2 permeabilities decreased by ∼9 % and ∼30 % relative to the pristine CMS membrane, both deviating notably from the upper bound slope trends. Gas diffusivity and pore size distribution analyses suggested that these improvements stemmed from a reduction in larger ultramicropores. Furthermore, a prolonged CO 2 /CH 4 mixed-gas permeation test (170 days) showed that pre-crosslinked CMS membranes demonstrated enhanced resistance to physical aging. After the aging period, the pre-crosslinked CMS membranes showed slightly higher mixed-gas CO 2 permeability and ∼2 times higher mixed-gas CO 2 /CH 4 selectivity than pristine CMS. This study introduces a novel method for tuning the CMS microstructure to produce more selective and aging-resistant carbon membranes. • New CMS membranes were fabricated from UV-crosslinkable PI precursors. • UV crosslinking of PI precursor effectively tunes the formation of larger ultramicropores. • Improves the molecular sieving properties and resistance to physical aging.

Source: Journal of Membrane Science

DOI: 10.1016/j.memsci.2025.124080