Hydrogen bonding structure of confined water templated by a metal-organic framework with open metal sites

Abstract

Water in confinement exhibits properties significantly different from bulk water due to frustration in the hydrogen-bond network induced by interactions with the substrate. Here, we combine infrared spectroscopy and many-body molecular dynamics simulations to probe the structure and dynamics of confined water as a function of relative humidity within a metal-organic framework containing cylindrical pores lined with ordered cobalt open coordination sites. Building upon the agreement between experimental and theoretical spectra, we demonstrate that water at low relative humidity binds initially to open metal sites and subsequently forms disconnected one-dimensional chains of hydrogen-bonded water molecules bridging between cobalt atoms. With increasing relative humidity, these water chains nucleate pore filling, and water molecules occupy the entire pore interior before the relative humidity reaches 30%. Systematic analysis of rotational and translational dynamics indicates heterogeneity in this pore-confined water, with water molecules displaying variable mobility as a function of distance from the interface.

Structure and solvation of confined water and water–ethanol clusters within microporous Brønsted acids and their effects on ethanol dehydration catalysis

“…The different solvation of MARI and transition states by water networks prevails among Brønsted acid zeolites of different topology (FAU, TON, MFI, CHA, AEI), whose micropore shapes inuence the severity of H 2 O inhibition by inuencing the ease of solvent reorganization within channel or windowcage motifs. Similar extended H-bonded H 2 O structures have also been identied within the pores of hydrophilic metalorganic frameworks 125,126 whose diverse topologies may stabilize an even broader range of solvent structures. The theoretical techniques developed here enable more direct comparison with experimental kinetics using solvent models based on locally stable phases at catalyst active sites.…”

Rational incorporation of defects within metal–organic frameworks generates highly active electrocatalytic sites

“…Further, OH bands of water molecules interacting with Mg-, Co-and Ni-MOF74 have been observed in this region and the red-shi relative to free H 2 O in the electrolyte suggests the presence of a strong hydrogen bonding network. [71][72][73] As the potential was increased further to 1.7 V, a positive band arose at 3100 cm À1 , here attributed to *OH adsorbing onto Ni sites as part of the OER cycle. In the same potential range, rst a band at 1546 cm À1 appeared at potentials prior to the catalytic onset, having a position matching that of the intermediate band from the open circuit measurements in Fig.…”

Atomistic insight in the flexibility and heat transport properties of the stimuli-responsive metal–organic framework MIL-53(Al) for water-adsorption applications using molecular simulations

“…Therefore, explicit electronic polarization is commonly not taken into account when studying water in confinement. 62,63 In spite of these limitations of a mean-field description of the polarization, this water model does allow to describe hydrogen bonding effects, as discussed in the Supporting Information (Section S1).…”

“…Finally, we also try to obtain molecular-level insight into the water structure inside the pores, which is currently an active field of research for water-stable MOFs. 58,60,[62][63][64][65] Using advanced molecular simulation tools on the prototypical flexible material MIL-53(Al), this work thus considers two important fundamental issues strongly related to water-adsorption applications of MOFs: (1) the phase stability and the water structure inside the pores of a stimuli-responsive MOF and (2) the anisotropic thermal conductivity properties of the adsorbent.…”