Capturing the H 2 –Metal Interaction in Mg-MOF-74 Using Classical Polarization

Type
Article

Authors
Pham, Tony
Forrest, Katherine A.
McLaughlin, Keith
Eckert, Juergen
Space, Brian

KAUST Grant Number
FIC/2010/06

Online Publication Date
2014-09-17

Print Publication Date
2014-10-02

Date
2014-09-17

Abstract
© 2014 American Chemical Society. Grand canonical Monte Carlo (GCMC) simulations of H2 sorption were performed in Mg-MOF-74, a metal-organic framework (MOF) that displays very high H2 sorption affinity. Experimental H2 sorption isotherms and isosteric heats of adsorption (Qst) values were reproduced using a general purpose materials sorption potential that includes many-body polarization interactions. In contrast, using two models that include only charge-quadrupole interactions failed to reproduce such experimental measurements even though they are the type normally employed in such classical force field calculations. Utilizing the present explicit polarizable model in GCMC simulation resulted in a Mg2+-H2 distance of 2.60 Å, which is close to a previously reported value that was obtained using electronic structure methods and comparable to similar experimental measurements. The induced dipole distribution obtained from simulation assisted in the characterization of two previously identified sorption sites in the MOF: the Mg2+ ions and the oxido group of the linkers. The calculated two-dimensional quantum rotational levels for a H2 molecule sorbed onto the Mg2+ ion were in good agreement with experimental inelastic neutron scattering (INS) data. Although the H2-metal interaction in MOFs may be thought of as a quantum mechanical effect, this study demonstrates how the interaction between the sorbate molecules and the open-metal sites in a particular highly sorbing MOF can be captured using classical simulation techniques that involve a polarizable potential.

Citation
Pham T, Forrest KA, McLaughlin K, Eckert J, Space B (2014) Capturing the H 2 –Metal Interaction in Mg-MOF-74 Using Classical Polarization . The Journal of Physical Chemistry C 118: 22683–22690. Available: http://dx.doi.org/10.1021/jp508249c.

Acknowledgements
This work was supported by the National Science Foundation (Award CHE-1152362). Computations were performed under a XSEDE Grant (TG-DMR090028) to B.S. This publication is also based on work supported by Award FIC/2010/06, made by King Abdullah University of Science and Technology (KAUST). The authors also thank the Space Foundation (Basic and Applied Research) for partial support. The authors acknowledge the use of the services provided by Research Computing at the University of South Florida.

Publisher
American Chemical Society (ACS)

Journal
The Journal of Physical Chemistry C

DOI
10.1021/jp508249c

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