Abstract
Few hydrogen adsorbents balance high usable volumetric and gravimetric capacities. Although metal-organic frameworks (MOFs) have recently demonstrated progress in closing this gap, the large number of MOFs has hindered the identification of optimal materials. Here, a systematic assessment of published databases of real and hypothetical MOFs is presented. Nearly 500,000 compounds were screened computationally, and the most promising were assessed experimentally. Three MOFs with capacities surpassing that of IRMOF-20, the record-holder for balanced hydrogen capacity, are demonstrated: SNU-70, UMCM-9, and PCN-610/NU-100. Analysis of trends reveals the existence of a volumetric ceiling at ∼40 g H2 L−1. Surpassing this ceiling is proposed as a new capacity target for hydrogen adsorbents. Counter to earlier studies of total hydrogen uptake in MOFs, usable capacities in the highest-capacity materials are negatively correlated with density and volumetric surface area. Instead, capacity is maximized by increasing gravimetric surface area and porosity. This suggests that property/performance trends for total capacities may not translate to usable capacities.
Highlights
Few hydrogen adsorbents balance high usable volumetric and gravimetric capacities
Consistent with the computational predictions, IRMOF-20 was demonstrated experimentally to exhibit an uncommon combination of high usable volumetric (UV) and gravimetric capacities[1]
These metal-organic frameworks (MOFs) were downselected using an initial screen based on crystallographic properties and the Chahine rule[8] from a database of 493,458 MOFs described in Table 2 and in Supplementary Tables 1–10
Summary
Few hydrogen adsorbents balance high usable volumetric and gravimetric capacities. metal-organic frameworks (MOFs) have recently demonstrated progress in closing this gap, the large number of MOFs has hindered the identification of optimal materials. A recent study by the present authors identified MOFs that simultaneously exhibit high volumetric and gravimetric hydrogen densities from a database of 5309 real compounds[1]. Three MOFs with usable capacities surpassing that of IRMOF-20 have been demonstrated: SNU-70, UMCM-9, and PCN-610/NU-100.
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