Understanding Hydrogen Adsorption in Metal−Organic Frameworks with Open Metal Sites:  A Computational Study

Abstract

Recent experimental investigations show that the open metal sites may have a favorable impact on the hydrogen adsorption capacity of metal-organic frameworks (MOFs); however, no definite evidence has been obtained to date and little is known on the interactions between hydrogen and the pore walls of this kind of MOFs. In this work, a combined grand canonical Monte Carlo simulation and density functional theory calculation is performed on the adsorption of hydrogen in MOF-505, a recently synthesized MOF with open metal sites, to provide insight into molecular-level details of the underlying mechanisms. This work shows that metal-oxygen clusters are preferential adsorption sites for hydrogen, and the strongest adsorption of hydrogen is found in the directions of coordinatively unsaturated open metal sites, providing evidence that the open metal sites have a favorable impact on the hydrogen sorption capacity of MOFs. The storage capacity of hydrogen of MOF-505 at room temperature and moderate pressures is predicted to be low, in agreement with the outcome for hydrogen physisorption in other porous materials.

A Novel Bismuth‐Based Metal–Organic Framework for High Volumetric Methane and Carbon Dioxide Adsorption

“…All atoms in the MOF structure were described by an OPLS force field 17 with the exception of Bi atom, which was described by universal force field parameters 18 and oxygen atoms, for which the force-field parameters were taken from a literature value. 19 The simulation supercell contained six (2x1x3) unit cells with periodic boundary conditions. The fugacity has been calculated from the Peng-Robinson equation of state 20 and the MOF and the guest gas molecules were considered to be rigid.…”

Effective Thermal Conductivity of MOF-5 Powder under a Hydrogen Atmosphere

“…The GCMC calculation is performed in a static state, in which the adsorption heat is assumed to be completely released. Hence, we do not consider the chemical potential caused by changes in vibrational entropy, as mentioned in [11,12]. Then  is defined as…”

“…Zhang et al [11] simulated H2 adsorption in MOF-5 at 77 K at different pressures (0-1.0 bar) and obtained results that fit well with the experimental data; they then performed computer tomography on the MOF-5 at a molecular level. Yang et al [12] combined GCMC simulation and density functional theory in their study of hydrogen adsorption in MOF-505; they found that metal oxygen clusters are preferential adsorption sites for hydrogen.…”

Advances in the application of nanotechnology in enabling a ‘hydrogen economy’

“…In addition, MOFs can be used as templates to create artificial interlinked hydrogen nanocages. In a computational study of MOF-505 (Cu 2 (3,3 0 ,5,5 0 -biphenyltetracarboxylic group)), Yang and Zhong [140] showed that open metal sites of the metal oxygen clusters are preferential adsorption sites for hydrogen. Including such sites in the framework may have a favorable impact on the hydrogen sorption capacity.…”