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Diffusion of Carbon Dioxide and Nitrogen in the Small‐Pore Titanium Bis(phosphonate) Metal–Organic Framework MIL‐91 (Ti): A Combination of Quasielastic Neutron Scattering Measurements and Molecular Dynamics Simulations
Author(s) -
Pillai Renjith Sasimohanan,
Jobic Hervé,
Koza Michael Marek,
Nouar Farid,
Serre Christian,
Maurin Guillaume,
Ramsahye Naseem Ahmed
Publication year - 2017
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201700459
Subject(s) - quasielastic neutron scattering , thermal diffusivity , molecular dynamics , diffusion , chemistry , neutron scattering , chemical physics , inelastic neutron scattering , analytical chemistry (journal) , thermodynamics , scattering , computational chemistry , organic chemistry , physics , optics
The diffusivity of CO 2 and N 2 in the small‐pore titanium‐based bis(phosphonate) metal–organic framework MIL‐91(Ti) was explored by using a combination of quasielastic neutron scattering measurements and molecular dynamics simulations. These two techniques were used to determine the loading dependence of the self‐diffusivity, corrected and transport diffusivities of these two gases to complement our previously reported thermodynamics study, which revealed that this material was a promising candidate for CO 2 /N 2 separation. The calculated and measured diffusivities of both gases were shown to be of an order of magnitude sufficiently high, from 10 −9 to 10 −10 m 2 s −1 , and N 2 diffused faster than CO 2 through the small channel of MIL‐91(Ti). Consequently, the separation process does not involve any kinetic‐driven limitations. This study further revealed that the global diffusion mechanism involves motions of gases along the channels by a jump sequence, and the residence times for CO 2 in the region close to the specific PO ⋅⋅⋅ H ⋅⋅⋅ N zwitterionic sites are much higher than those for N 2 , which explains the faster diffusivity observed for N 2 .