Multidimensional pore design rules for SF6/N2 and CF4/N2 separation in zeolite-templated carbons

초록

Selective separation of potent fluorinated greenhouse gases, such as SF6 and CF4, from nitrogen (N2) constitutes a significant environmental and industrial challenge. Zeolite-templated carbons (ZTCs) are compelling carbon adsorbents due to their zeolite-derived three-dimensional microporosity, which can be systematically tailored. However, the structural foundations underlying their separation efficacy remain inadequately understood. Grand Canonical Monte Carlo (GCMC) simulations were conducted to evaluate 119 pristine ZTCs for the separation of SF6/N2 and CF4/N2 binary mixtures at 298 K and 1 bar. A total of 23 and 29 ZTCs were identified for SF6/N2 and CF4/N2 separations, respectively, exhibiting APS values superior to those of previously reported high-performance carbon adsorbents, including 19 frameworks that demonstrated proficiency in both mixture types. The high selectivity observed is primarily attributable to suppressed N2 uptake under competitive mixture conditions, wherein SF6 or CF4 preferentially occupy strongly confining adsorption domains, thereby limiting residual space for N2 co-adsorption. Multidimensional descriptor analysis elucidated optimal parameter ranges for the largest cavity diameter, pore-limiting diameter, framework density, and accessible volume fraction. Sequential filtering based on these parameters increased the proportion of high-performing candidates to 83% for SF6 and 73% for CF4. Topological analysis linked these local geometric features to zeolite-template motifs that generate recurrent, accessible confinement domains, rather than attributing selectivity to a single net. Models of defective ZTCs with reduced carbon density generally exhibited diminished performance due to removal and relaxation of carbon, which disrupted ideal confinement sites for fluorinated gas adsorption and, in some cases, generated microcavities accessible to N2. These findings elucidate how local geometric configurations, template topology, and defects collectively influence fluorinated-gas separation efficiency in ZTCs. © 2026 Elsevier B.V.

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