Exceptional hydrogen storage achieved by screening nearly half a million metal-organic frameworks

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 H 2 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.

An International Laboratory Comparison Study of Volumetric and Gravimetric Hydrogen Adsorption Measurements

“…However, there is a material‐dependent compression pressure in which the pore structure will collapse if the sample is compacted too much . Theoretical investigations have provided a path forward by correlating important physical parameters of materials (i. e. pore volume, surface area, volumetric surface area) with maximizing volumetric hydrogen capacities …”

The Chemistry of Porous Organic Molecular Materials

“…[277] There are some similarities between the use of ESF maps in materials discovery and the high-throughput screening of hypothetical MOFs structures for useful functions. [278][279][280][281] A key differece is that ESF maps for organic materials includes information on the predicted crystal lattice energy-effectively, the likely propensity for the structure to exist-which is not generally a feature in MOF structural screens. [282] The use of ESF maps in the discovery of functional organic crystals has also been used for materials, such as organic semiconductors.…”

Revealing the effect of structure curations on the simulated CO2 separation performances of MOFs

“…Results of computational studies are useful to direct experimental efforts, time and resources to the best performing materials. There are excellent examples in which promising MOFs identified by computational studies [4][5][6][7] were synthesized and experimentally tested. 4,5,8 For example, Ahmed et al 4 computationally screened nearly half a million MOFs for H 2 storage, and proposed three MOFs that exceed the storage capacity of prototype MOF-5.…”

“…There are excellent examples in which promising MOFs identified by computational studies [4][5][6][7] were synthesized and experimentally tested. 4,5,8 For example, Ahmed et al 4 computationally screened nearly half a million MOFs for H 2 storage, and proposed three MOFs that exceed the storage capacity of prototype MOF-5. They demonstrated a perfect agreement between experiments and simulations for both gravimetric and volumetric H 2 adsorption isotherms of these MOFs up to 100 bar at 77 K. Moghadam et al 5 performed a computational study to screen almost 3000 MOFs to predict their deliverable O 2 capacities, and experimentally synthesized and tested one of the top materials.…”