Effect of Metal-Organic Framework (MOF) Database Selection on the Assessment of Gas Storage and Separation Potentials of MOFs

Abstract

Development of computation-ready metal-organic framework databases (MOF DBs) has accelerated high-throughput computational screening (HTCS) of materials to identify the best candidates for gas storage and separation. These DBs were constructed using structural curations to make MOFs directly usable for molecular simulations, which caused the same MOF to be reported with different structural features in different DBs. We examined thousands of common materials of the two recently updated, very widely used MOF DBs to reveal how structural discrepancies affect simulated CH₄ , H₂ , CO₂ uptakes and CH₄ /H₂ separation performances of MOFs. Results showed that DB selection has a significant effect on the calculated gas uptakes and ideal selectivities of materials at low pressure. A detailed analysis on the curated structures was provided to isolate the critical elements of MOFs determining the gas uptakes. Identification of the top-performing materials for gas separation was shown to strongly depend on the DB used in simulations.

Keywords: adsorption; database; high-throughput screening; metal-organic frameworks (MOFs); molecular modelling.

Figure 1

${\mathrm{K}}_{{\mathrm{H}}_2}$ , ${\mathrm{K}}_{\mathrm{C}{\mathrm{H}}_4}$ computed at a) infinite dilution, ${\mathrm{N}}_{{\mathrm{H}}_2}$ , ${\mathrm{N}}_{{\mathrm{CH}}_4}$ computed at b) 1 bar, c) 20 bar, and d) 65 bar for 1109 CFU‐MOFs of two DBs. Red symbols represent CH₄, black symbols represent H₂ data.

Figure 2

Relation between PV_ratio and S_{acc, ratio} of 1109 CFU‐MOFs. Data is color‐coded according to K${}_{\mathrm{CH}{}_4,\mathrm{ratio}}$ computed at a) infinite dilution, N${}_{\mathrm{CH}{}_4,\mathrm{ratio}}$ computed at b) 1 bar, c) 20 bar, d) 65 bar. A, B and C on color code represents the groups of MOFs whose examples are shown in Table S2.

Figure 3

a) S_mix computed at 10 bar, b) APS, c) R% of 1109 CFU‐MOFs (black), and 2434 CFM‐MOFs (purple) at PSA condition. Blue and red symbols in (c) represent the top 10 MOFs of two DBs. d) APS_ratio and R%_ratio of 1109 CFU‐MOFs computed at PSA condition.

Figure 4

Elemental differences between 1109 CFU‐MOFs of two DBs. Colors represent a) N${}_{\mathrm{H}{}_2,\mathrm{ratio}}$ , b) N${}_{\mathrm{CH}{}_4,\mathrm{ratio}}$ , c) N${}_{\mathrm{CO}{}_2,\mathrm{ratio}}$ of MOFs at 1 bar.

Figure 5

Analysis of the relationship between structural differences of MOFs in two DBs and their effects on CH₄ and H₂ uptakes of CFU‐MOFs at 1 bar. − represents the single bond = represents the double bond. Size of circles represents the average of N${}_{\mathrm{CH}{}_4,\mathrm{ratio}}$ Size of diamonds represents the average(N${}_{\mathrm{H}{}_2,\mathrm{ratio}}$ ).