Abstract
A combined inelastic neutron scattering (INS) and theoretical study of H2 sorption was performed in PCM-16, a phosphine coordination material (PCM) with the empirical formula [(CH3)2NH2][Dy2(tctpo)2(O2CH)] (tctpo = tris(p-carboxylato)triphenylphosphine oxide). INS measurements at different loadings of H2 revealed a peak occurring at low rotational tunnelling energies (ca. 5-8 meV), which corresponds to a high barrier to rotation and, therefore, a strong interaction with the host. Molecular simulations of H2 sorption in PCM-16 revealed that the H2 molecules sorbed at two main sites in the material: (1) the (CH3)2NH2+ counterions and (2) within the small pores of the framework. Two-dimensional quantum rotation calculations revealed that the peak occurring from approximately 5-8 meV in the INS spectra for PCM-16 is associated with sorption onto the (CH3)2NH2+ ions. These counterions provide for the strongest H2 sorption sites in the material, which corresponds to an isosteric heat of adsorption (Qst) value of close to 8 kJ mol-1. The calculated rotational barrier for the (CH3)2NH2+-H2 interaction in PCM-16 (45.60 meV) is higher than those for a number of extant metal-organic frameworks (MOFs), especially those that contain open-metal sites. This study provides insights into the H2 sorption mechanism in a PCM for the first time and shows how the inclusion of counterions in porous materials is a promising method to increase the H2 sorption energetics in such materials.
Original language | English (US) |
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Pages (from-to) | 7619-7626 |
Number of pages | 8 |
Journal | CHEMISTRY OF MATERIALS |
Volume | 27 |
Issue number | 22 |
DOIs | |
State | Published - 2015 |
Externally published | Yes |
Bibliographical note
KAUST Repository Item: Exported on 2021-11-05Acknowledged KAUST grant number(s): FIC/2010/06
Acknowledgements: B.S. acknowledges the National Science Foundation (Award No. CHE-1152362), the computational resources that were made available by a XSEDE Grant (No. TG-DMR090028), and the use of the services provided by Research Computing at the University of South Florida. This publication is also based on work supported by Award No. FIC/2010/06, made by King Abdullah University of Science and Technology (KAUST). P.A.G. acknowledges support from the Project Beyond Everest under EU programme REGPOT-2011-1. This research project was also supported by the European Commission under the 7th Framework Programme through the Research Infrastructures action of the Capacities Programme, NMI3-II Grant No. 283883. S.M.H. acknowledges funding from the National Science Foundation (Award No. DMR-1506994) and the Welch Foundation (F-1738).
This publication acknowledges KAUST support, but has no KAUST affiliated authors.
ASJC Scopus subject areas
- Materials Chemistry
- General Chemical Engineering
- General Chemistry