Understanding the H₂ Sorption Trends in the M-MOF-74 Series (M = Mg, Ni, Co, Zn)

Abstract

Electronic structure calculations and simulations of H 2 sorption were performed in four members of the M-MOF-74 series: Mg-MOF-74, Ni-MOF-74, Co-MOF-74, and Zn-MOF-74. Notable differences were observed in the partial charge and polarizability of the metal ions derived from the electronic structure calculations. The modeling parameters obtained from the electronic structure calculations were found to influence certain features in the experimentally observed H 2 sorption trends in the M-MOF-74 series. The simulations were performed with the inclusion of explicit many-body polarization, which was required to reproduce the experimental H 2 sorption observables (i.e., sorption isotherms and isosteric heats of adsorption (Q st )) and the H 2 −metal interaction in all four MOFs using classical molecular simulation. Consistent with experimental measurements, the simulations captured the following trend for the H 2 −metal interaction strength: Ni-MOF-74 > Co-MOF-74 > Mg-MOF-74 > Zn-MOF-74. The calculations revealed that stronger H 2 −metal interactions within the M-MOF-74 series corresponded to shorter H 2 −metal distances and higher induced dipoles on the metal-sorbed H 2 molecules. In addition, it was observed that there was a strong correlation between the H 2 −metal interaction and the polarization contribution. Although Mg-MOF-74 has the highest calculated partial charge for the metal ion within the series, the Mg 2+ ion has a very low polarizability compared to the other M 2+ ions; this explains why the H 2 −metal interaction in this MOF is weaker compared to those for Ni-MOF-74 and Co-MOF-74. The sterics interactions, reflected in the crystal structure for all four MOFs, also played a role for the observed H 2 sorption trends. Zn-MOF-74 has the lowest H 2 uptakes and Q st within the series due to an unfavorable geometric environment for the Zn 2+ ions within the ZnO 5 clusters. Lastly, the two-dimensional quantum rotational levels were calculated for the H 2 −metal interaction in all four MOFs using the potential energy function employed herein and the calculated transitions were in good agreement with the corresponding peaks that were observed in the experimental inelastic neutron scattering (INS) spectra for the respective MOFs. This observation serves both to provide atomistic resolution to the spectroscopic experiments and to validate the molecular force field.

Synthesis of 9,9′-spirobifluorene-based conjugated microporous polymers by FeCl3-mediated polymerization

“…However, the H 2 uptake at 77 K by COP-3-600 (2.2 wt%) was found to be lower than that of activated carbon (2.8 wt%, 1 bar), 23 but comparable with those of poly(vinylidene chloride)-based carbon (2.5 wt%,) 24 and MOF-74s (1.8-2.5 wt%). 25 In addition, the reusability of the samples for CO 2 adsorption was confirmed by recycling experiments ( Figure S14). …”

[Mo3S13]2− Cluster Decorated Sulfur‐doped Reduced Graphene Oxide as Noble Metal‐Free Catalyst for Hydrogen Evolution Reaction in Polymer Electrolyte Membrane Electrolyzers

“…The activity improvements of Mo 3 S 13 -SrGO800 and Mo 3 S 13 -SrGO1000 as compared to Mo 3 S 13 -SrGO500 and Mo 3 S 13 -SrGO150 might be attributed to the higher electrical conductivity of SrGO800 and SrGO1000 as result of the higher reduction temperature. However, smaller contents of doped S and O (see Table S1, SI) make SrGO1000 less solution-dispersible due to the restacking property of graphene layers and less anchor points for [Mo 3 S 13 ] 2À attachment, [16] which in turn lead to an inverse effect on the HER activity of the resulting hybrid. This explains the slightly less activity of Mo 3 S 13 -SrGO1000 as compared to Mo 3 S 13 -SrGO800.…”

“…However, once rGO is synthesized by reducing graphene oxide (GO), the graphene sheets are often restacking together, making further processing difficult. [16] Moreover, the non-polar property of graphene surface is not compatible with [Mo 3 S 13 ] 2À , which might lead to an unstable hybrid between the two materials. To overcome these challenges, in the current work, instead of rGO, we used S-doped reduced graphene oxide (SrGO) as support for the [Mo 3 S 13 ] 2À catalyst.…”

Understanding Hydrogen Sorption in In-soc-MOF: A Charged Metal-Organic Framework with Open-Metal Sites, Narrow Channels, and Counterions

“…The development of the force field for In-soc-MOF was performed according to the procedure described in previous work. 12,24,25,[29][30][31][32][33][34][35][36][37][38][39][40][41] Nevertheless, a brief outline is given here. For all C, H, and N atoms on the organic linker in In-soc-MOF, the Lennard-Jones 12-6 parameters, representing van der Waals interactions between the sorbate molecules and the MOF atoms, were acquired from the Optimized Potentials for Liquid Simulations -All Atom (OPLS-AA) force field.…”