Engineering carbon molecular sieve membranes with tailored microstructures via molecular doping for superior hydrogen separation

Carbon molecular sieve (CMS) membranes present significant advantages and considerable potential for the precise separation of hydrogen gas, promoting the utilization of clean hydrogen energy. Recently, molecular or atomic-level doping exhibits a strong capacity to adjust the structure and performance of CMS membranes. However, there is limited understanding of how fine-tuning through molecular doping can adjust the physical properties of the microscopic carbon structures within CMS membranes. In this study, small molecule siloxanes are incorporated into precursor to facilitate the in-situ formation of silicon-doped CMS membranes at the molecular level. Interestingly, by modulating the side groups of the siloxanes, we can selectively adjust the morphology and size of the micro-carbon sheets within CMS membranes, thereby enabling precise tuning of the pore structure, separation performance and anti-aging ability. The resulting CMS membranes exhibit exceptional H 2 /CH 4 separation capabilities, significantly surpassing 2015 upper bounds. Besides, silicon-based functional groups and enlarged carbon structure effectively inhibit the physical aging of CMS membranes. This insight offers a more nuanced and controlled approach to precisely tailor microstructure of CMS membranes for efficient H 2 separation.