High-Performance Hybrid CMS Membranes Development via Synergistic Pore Tailoring and Sulfur-Doping

Precisely tailoring the micro-structure of hybrid carbon molecular sieve (HCMS) membranes is of critical importance to enhance their gas separation performance. Herein, an organic acid, methanesulfonic acid (MSA), was employed as a porogen and dopant of sulfone in CMS membranes. MSA acted as a porogen to generate abundant micropores (enhancing diffusivity), meanwhile the presence of MSA turned the pore structure (promoting selectivity). Theoretical calculations confirmed that the S-doped pore environment exhibited superior affinity toward CO₂. The resulting 6FDA-TMPD/MSA-5-500 HCMS membrane displayed an ultra-high CO₂ permeability of 10557.6 Barrer (representing a ∼150-fold enhancement over its precursor) and a CO₂/CH₄ selectivity of 29.1, surpassing the latest Robeson upper bound. Moreover, the MSA-mediated cross-linking structure promoted the formation of more ordered Langmuir domains and reduced the d-spacing as well as ultramicropore sizes. Concurrently, precise tuning of carbonization parameters further enriched the population of ultramicropores within the size range between H₂ (2.9 Å) and CO₂ (3.3 Å). Specifically, the 6FDA-TMPD/MSA-5-700 HCMS membrane presented a H₂/CH₄ selectivity of 539.0 coupled with a H₂ permeability of 2421.9 Barrer. This work synchronously modulates the pore structure and surface chemical properties of CMS membranes, providing new references for the preparation of high-performance CMS membranes for gas separation.