TY - JOUR

T1 - Water Dynamics in NH2-MIL-125: Insights from a Combined1H NMR Relaxometry and Computational Investigation

AU - Pizzanelli, Silvia

AU - Freni, Angelo

AU - Farmahini, Amir H.

AU - Gordeeva, Larisa G.

AU - Sarkisov, Lev

AU - Solovyeva, Marina V.

AU - Forte, Claudia

N1 - Funding Information: S.P. and C.F. would like to acknowledge the contribution of the COST Action CA15209 (Eurelax: European Network on NMR Relaxometry). L.G. and M.S. thank the Russian Foundation for Basic Research for partial support of this study (grant no. 18-29-04033). L. S. would like to thank Prof. Guillaume Maurin for the simulation-ready cif file for NH-MIL-125 and useful comments. 2 Publisher Copyright: © 2021 American Chemical Society

PY - 2021/7/8

Y1 - 2021/7/8

N2 - The dynamics of water confined in a microporous metal-organic framework was investigated by1H fast field-cycling nuclear magnetic resonance (NMR) relaxometry, exploring time scales ranging between 10 μs and 0.1 ns in the 25-80 °C temperature interval. The data were interpreted within a dynamic model where molecules bind to the surface hopping among preferential binding sites. The bound molecules are also subject to local faster reorientations. Numerical analysis of the data allowed the characteristic times associated with hops and local anisotropic reorientations to be determined together with their activation energies, as derived through Arrhenius fits. The values of the activation energies, 16 ± 2 and 4.5 ± 0.5 kJ/mol, respectively, were rationalized within the model.1H magic-angle spinning NMR was used to quantify the water loading level and to obtain evidence on the presence of bound water molecules as required by the dynamic model, whereas molecular simulations were conducted to obtain complementary information on relevant properties, such as the porosity of the matrix, the water binding sites, self-diffusion, and interaction energies in the confined space.

AB - The dynamics of water confined in a microporous metal-organic framework was investigated by1H fast field-cycling nuclear magnetic resonance (NMR) relaxometry, exploring time scales ranging between 10 μs and 0.1 ns in the 25-80 °C temperature interval. The data were interpreted within a dynamic model where molecules bind to the surface hopping among preferential binding sites. The bound molecules are also subject to local faster reorientations. Numerical analysis of the data allowed the characteristic times associated with hops and local anisotropic reorientations to be determined together with their activation energies, as derived through Arrhenius fits. The values of the activation energies, 16 ± 2 and 4.5 ± 0.5 kJ/mol, respectively, were rationalized within the model.1H magic-angle spinning NMR was used to quantify the water loading level and to obtain evidence on the presence of bound water molecules as required by the dynamic model, whereas molecular simulations were conducted to obtain complementary information on relevant properties, such as the porosity of the matrix, the water binding sites, self-diffusion, and interaction energies in the confined space.

UR - http://www.scopus.com/inward/record.url?scp=85110321366&partnerID=8YFLogxK

U2 - 10.1021/acs.jpcc.1c02045

DO - 10.1021/acs.jpcc.1c02045

M3 - Article

AN - SCOPUS:85110321366

VL - 125

SP - 14416

EP - 14429

JO - Journal of Physical Chemistry C

JF - Journal of Physical Chemistry C

SN - 1932-7447

IS - 26

ER -