TY - JOUR

T1 - Mobility of Aromatic Guests and Isobutane in ZIF-8 Metal-Organic Framework Studied by 2H Solid State NMR Spectroscopy

AU - Khudozhitkov, Alexander E.

AU - Arzumanov, Sergei S.

AU - Kolokolov, Daniil I.

AU - Stepanov, Alexander G.

PY - 2019/6/6

Y1 - 2019/6/6

N2 - Metal-organic framework ZIF-8 is renowned for its adsorption and separation properties influenced by the framework flexibility. Although much effort was put into understanding the molecular mechanism of such gate-opening (dynamical and static), the mobility of large guest themselves remained unclear. In this work, we present a detailed 2H solid-state NMR investigation of large guests (xylene isomers, benzene, toluene, and isobutane) confined inside the ZIF-8. Evolution of line shape and T1, T2 relaxation times with temperature were interpreted in terms of existence of three different motional states for diffusing guest molecules: (i) the highly mobile guest molecules located in the central part of the cage; (ii) the bound state for a guest located on the cage wall or near the window; and (iii) the guest squeezing through the window with a subsequent release to the next cage. We report detailed quantitative analysis of molecular dynamics in each of the states and the kinetics of exchange between the bound and mobile states.

AB - Metal-organic framework ZIF-8 is renowned for its adsorption and separation properties influenced by the framework flexibility. Although much effort was put into understanding the molecular mechanism of such gate-opening (dynamical and static), the mobility of large guest themselves remained unclear. In this work, we present a detailed 2H solid-state NMR investigation of large guests (xylene isomers, benzene, toluene, and isobutane) confined inside the ZIF-8. Evolution of line shape and T1, T2 relaxation times with temperature were interpreted in terms of existence of three different motional states for diffusing guest molecules: (i) the highly mobile guest molecules located in the central part of the cage; (ii) the bound state for a guest located on the cage wall or near the window; and (iii) the guest squeezing through the window with a subsequent release to the next cage. We report detailed quantitative analysis of molecular dynamics in each of the states and the kinetics of exchange between the bound and mobile states.

KW - ZEOLITIC IMIDAZOLATE FRAMEWORKS

KW - DEUTERIUM NMR

KW - SEPARATION

KW - ADSORPTION

KW - CO2

KW - DIFFUSION

KW - MIXTURES

KW - DYNAMICS

KW - TEMPERATURE

KW - ADSORBENTS

UR - http://www.scopus.com/inward/record.url?scp=85067125793&partnerID=8YFLogxK

U2 - 10.1021/acs.jpcc.9b03081

DO - 10.1021/acs.jpcc.9b03081

M3 - Article

AN - SCOPUS:85067125793

VL - 123

SP - 13765

EP - 13774

JO - Journal of Physical Chemistry C

JF - Journal of Physical Chemistry C

SN - 1932-7447

IS - 22

ER -