Computational Screening of MOFs for Acetylene Separation

Efficient separation of acetylene (C(2)H(2)) from CO(2) and CH(4) is important to meet the requirement of high-purity acetylene in various industrial applications. Metal organic frameworks (MOFs) are great candidates for adsorption-based C(2)H(2)/CO(2) and C(2)H(2)/CH(4) separations due to their unique properties such as wide range of pore sizes and tunable chemistries. Experimental studies on the limited number of MOFs revealed that MOFs offer remarkable C(2)H(2)/CO(2) and C(2)H(2)/CH(4) selectivities based on single-component adsorption data. We performed the first large-scale molecular simulation study to investigate separation performances of 174 different MOF structures for C(2)H(2)/CO(2) and C(2)H(2)/CH(4) mixtures. Using the results of molecular simulations, several adsorbent performance evaluation metrics, such as selectivity, working capacity, adsorbent performance score, sorbent selection parameter, and regenerability were computed for each MOF. Based on these metrics, the best adsorbent candidates were identified for both separations. Results showed that the top three most promising MOF adsorbents exhibit C(2)H(2)/CO(2) selectivities of 49, 47, 24 and C(2)H(2)/CH(4) selectivities of 824, 684, 638 at 1 bar, 298 K and these are the highest C(2)H(2) selectivities reported to date in the literature. Structure-performance analysis revealed that the best MOF adsorbents have pore sizes between 4 and 11 Å, surface areas in the range of 600–1,200 m(2)/g and porosities between 0.4 and 0.6 for selective separation of C(2)H(2) from CO(2) and CH(4). These results will guide the future studies for the design of new MOFs with high C(2)H(2) separation potentials.