Fine-Tuning Sub-Ångström Pores in Carbon Molecular Sieve Membranes via UV-Crosslinking Induced Super-Network Polyimide Precursors for Ultra-Selective H2 Purification

Achieving precise customization and structural regulation of sub-Ångström pores of Carbon molecular sieve membranes (CMSMs) remains challenging. In this study, CMSMs with ultra-high H 2 /CH 4 separation performance were developed by a UV induced super-crosslinking network polyimide precursor, which was formed by click reaction through an imide intermediate that contains C≡CH and the SH as functional end groups. The as-formed polyimide contains C═C─S in each repeat unit of the polyimide which can be crosslinked using UV light via the [2+2] reaction and form molecular “stitches” with a super-crosslinking network. The cross-linking node density can be easily adjusted by the UV irradiation time (0–30 min). During pyrolysis, the dimensions of the connecting interior pore necks for sub-Ångström pores can be fine-tuned (4.0±0.3 Å), promoting the formation of a higher concentrated (4%–8%) sub-4 Å pores. The optimized CMS-30 membrane demonstrates outstanding gas separation performance, with H 2 permeability of 2930 Barrer and remarkable selectivity for H 2 /CH 4 (4651), surpassing the Robeson upper bounds and outperforming most reported CMSMs. This photo-induced super-crosslinking network precursor method provides a versatile strategy for high-performance CMSM by sub-nanometer precision engineering of CMSMs.