Influence of Structural Domain Evolution in Carbon Materials on the Selective Separation of Alkenes from Alkanes

Highly selective separation of alkenes/alkanes at ambient conditions is crucial yet challenging in the petrochemical industry due to their similar physical properties and molecular sizes. The development of carbon adsorbents that possess a molecular sieve functionality is desirable. In this study, we focus on elucidating the effect of carbonaceous nanodomain evolution on the pore sizes for the selective sieving separation of alkenes/alkanes using sucrose-based carbon molecular sieves (SUC-x). Results show that the carbonaceous nanodomains evolved gradually toward a more orderly graphitic layer structure at elevated temperatures, promoting the shrinkage of ultramicropores at the subangstrom scale. SUC-900 exhibits the C3H6/C3H8 molecular sieving performance with a high C3H6 uptake of 2.0 mmol/g at 1.0 bar and 298 K and negligible C3H8 adsorption, achieving a molecular recognition precision of 0.4 Å. The breakthrough experiments further confirm the efficient separation of the C3H6/C3H8 mixture dynamically in the fixed bed packed with SUC-900. This study provides a significant guideline for the precise tuning of ultramicropore sizes in carbons by manipulating structural nanodomains, facilitating the design of diverse carbon materials for gas separation applications.