TY - JOUR
T1 - Inelastic Neutron Scattering and Theoretical Studies of H2 Sorption in a Dy(III)-Based Phosphine Coordination Material
AU - Forrest, Katherine A.
AU - Pham, Tony
AU - Georgiev, Peter A.
AU - Embs, Jan Peter
AU - Waggoner, Nolan W.
AU - Hogan, Adam
AU - Humphrey, Simon M.
AU - Eckert, Juergen
AU - Space, Brian
N1 - Publisher Copyright:
© 2015 American Chemical Society.
Copyright:
Copyright 2015 Elsevier B.V., All rights reserved.
PY - 2015/10/22
Y1 - 2015/10/22
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=84947976436&partnerID=8YFLogxK
U2 - 10.1021/acs.chemmater.5b02747
DO - 10.1021/acs.chemmater.5b02747
M3 - Article
AN - SCOPUS:84947976436
VL - 27
SP - 7619
EP - 7626
JO - Chemistry of Materials
JF - Chemistry of Materials
SN - 0897-4756
IS - 22
ER -