Do New MOFs Perform Better for CO₂ Capture and H₂ Purification? Computational Screening of the Updated MOF Database

Abstract

High-throughput computational screening of metal organic frameworks (MOFs) enables the discovery of new promising materials for CO 2 capture and H 2 purification. The number of synthesized MOFs is increasing very rapidly, and computation-ready, experimental MOF databases are being updated. Screening the most recent MOF database is essential to identify the best performing materials among several thousands. In this work, we performed molecular simulations of the most recent MOF database and described both the adsorbent and membrane-based separation performances of 10 221 MOFs for CO 2 capture and H 2 purification. The best materials identified for pressure swing adsorption, vacuum swing adsorption, and temperature swing adsorption processes outperformed commercial zeolites and previously studied MOFs in terms of CO 2 selectivity and adsorbent performance score. We then discussed the applicability of Ideal Adsorbed Solution Theory (IAST), effects of inaccessible local pores and catenation in the frameworks and the presence of impurities in CO 2 /H 2 mixture on the adsorbent performance metrics of MOFs. Very large numbers of MOF membranes were found to outperform traditional polymer and porous membranes in terms of H 2 permeability. Our results show that MOFs that are recently added into the updated MOF database have higher CO 2 /H 2 separation potentials than the previously reported MOFs. MOFs with small pores were identified as potential adsorbents for selective capture of CO 2 from H 2 , whereas MOFs with high porosities were the promising membranes for selective separation of H 2 from CO 2 . This study reveals the importance of enriching the number of MOFs in high-throughput computational screening studies for the discovery of new promising materials for CO 2 /H 2 separation.

Metal Exchange Boosts the CO2 Selectivity of Metal Organic Frameworks Having Zn-Oxide Nodes

“…We recently performed high-throughput computational screening of 10,221 MOFs retrieved from the Cambridge Structural Database (CSD) 28 for CO 2 /H 2 separation and showed that MOFs perform well as CO 2 adsorbents. 29 In this work, we first utilized CSD ConQuest software 30 and conducted a connectivity search on these 10,221 MOFs. The guidelines described in the literature 27 were followed for targeted classification of MOFs, and 933 MOFs with Zn-oxide nodes were identified.…”

“… 25 We aimed to work on relatively simple MOF structures and eliminated the MOFs consisting of mixed linkers and/or functional groups due to the following reasons: (i) MOFs designed with mixed linker strategies can have defects, 31 , 32 or differing topologies and crystal structures, 33 but we aimed to work on MOFs with similar topologies after metal exchange and with a defect-free, homogeneous adsorption surface. (ii) MOFs with functional groups can have strong electrostatic interactions with CO 2 as shown in our previous works 29 , 34 but we aimed to isolate the influence of metal exchange on CO 2 /H 2 and CO 2 /CH 4 selectivity by omitting the MOFs with functional groups and mixed linkers. 769 MOFs with Zn-oxide nodes, a single type of linker, and no functional groups were divided into two final subgroups depending on the shape of the metal cluster (coordination of the node): 140 IRMOF-like MOFs (IRMOFs) and remaining (629) MOFs with Zn-oxide nodes (ZnO-MOFs).…”

“… 36 , 37 We considered pore sizes between 3.3 and 4 Å as small, 4 and 20 Å as mediocre, and 20 and 45 Å as large by following the convention used in our previous study. 29 We selected SAHYIK as a benchmark MOF because several previous works have both experimentally and computationally performed metal exchange on IRMOF series. 13 , 38 − 40 For example, Ti, V, Cr, Mn, Fe, and Ni variants of MOF-5 were experimentally reported via cation exchange.…”

Recent advances in simulating gas permeation through MOF membranes

“…Due to a wide range of chemical environments and high porosities of MOFs, gas permeability and membrane selectivity of MOFs have been reported in a very large range. [97][98][99] In addition, when molecular sieving mechanism is used to assess the gas separation performances of MOF, extremely high membrane selectivities (up to 10 8 ) are reported in the literature. 72 For these reasons, it is difficult to observe a trade-off or define the upper-performance limits of MOF membranes.…”

Trends and Prospects in UiO‐66 Metal‐Organic Framework for CO2 Capture, Separation, and Conversion

“…Inspired by the advancements mentioned above and by the vast available literature on UiO‐66 MOF as illustrated in Figure 3, the current review, therefore, focuses on UiO‐66 MOFs for CO 2 capture, separation and conversion applications. Although there are numerous papers and reviews covering MOFs applied to CO 2 capture, separation, and conversion [15,71–80] . However, this review′s importance lies particularly in the versatility of the pristine, functionalized and composites of UiO‐66 MOFs materials covering the literature from 2008 to 2020.…”