Open metal sites govern hydration kinetics and molecular fluctuations in metal–organic frameworks
Citation Link: https://doi.org/10.15480/882.17441
Publikationstyp
Journal Article
Date Issued
2026-07-01
Sprache
English
TORE-DOI
Volume
130
Issue
28
Start Page
9787
End Page
9801
Citation
The Journal of Physical Chemistry C 130 (28): 9787−9801 (2026)
Publisher DOI
Scopus ID
Publisher
American Chemical Society (ACS)
Water under nanoscale confinement exhibits structural and dynamical states distinct from bulk behavior, yet the role of pore chemistry in governing these states remains insufficiently understood. Herein, the hydration kinetics and molecular-scale fluctuations of water confined within a comprehensive series of MOF-74 metal-organic frameworks incorporating Mg, Ni, Co, and mixed-metal compositions were investigated and compared with those observed in mesoporous MCM-41 silica. In situ impedance pectroscopy resolves a pronounced multistep hydration mechanism in MOF-74, initiated by rapid coordinative binding at open metal sites, followed by cluster formation and final capillary condensation. In contrast to MCM-41 silica, where capillary condensation dominates, the presence of coordinatively unsaturated metal centers fundamentally alters adsorption pathways. Mixedmetal MOF-74 exhibits accelerated and temporally broadened hydration, reflecting heterogeneous distributions of adsorption
energies. Broadband dielectric spectroscopy reveals a distinct water-specific relaxation process (w-relaxation) attributed to fluctuations of water clusters interacting with metal nodes. Relaxation rates follow Arrhenius behavior with activation energies
increasing in the order Mg < Ni < Co and further enhanced in mixed-metal systems. Remarkably, water confined within MOF-74 remains liquid-like down to 133 K without crystallization, whereas crystallization is observed in MCM-41 silica. All activation data of
the MOF-74 systems obey a common Meyer−Neldel compensation relation, indicating cooperative molecular dynamics and suggesting a hindered glass-transition−like process of confined water clusters. These findings demonstrate that open metal sites and
metal composition enable programmable control over hydration kinetics and collective water dynamics in microporous frameworks. MOF-74 thus provides a tunable model platform for engineering water-driven transport, catalysis, and energy-relevant processes at the nanoscale.
energies. Broadband dielectric spectroscopy reveals a distinct water-specific relaxation process (w-relaxation) attributed to fluctuations of water clusters interacting with metal nodes. Relaxation rates follow Arrhenius behavior with activation energies
increasing in the order Mg < Ni < Co and further enhanced in mixed-metal systems. Remarkably, water confined within MOF-74 remains liquid-like down to 133 K without crystallization, whereas crystallization is observed in MCM-41 silica. All activation data of
the MOF-74 systems obey a common Meyer−Neldel compensation relation, indicating cooperative molecular dynamics and suggesting a hindered glass-transition−like process of confined water clusters. These findings demonstrate that open metal sites and
metal composition enable programmable control over hydration kinetics and collective water dynamics in microporous frameworks. MOF-74 thus provides a tunable model platform for engineering water-driven transport, catalysis, and energy-relevant processes at the nanoscale.
DDC Class
620.11: Engineering Materials
541.3: Physical Chemistry
Publication version
publishedVersion
Loading...
Name
open-metal-sites-govern-hydration-kinetics-and-molecular-fluctuations-in-metal-organic-frameworks.pdf
Size
3.64 MB
Format
Adobe PDF