Cluster Assisted Water Dissociation Mechanism in MOF-74 and Controlling it Using Helium

TL;DR

This study reveals how water dissociation in MOF-74 can be precisely controlled using helium, with implications for enhancing water stability in MOFs through understanding cluster formation and reaction barriers.

Contribution

The paper demonstrates that helium can suppress water cluster formation and dissociation in MOF-74, providing a novel method to control water-related reactions in MOFs.

Findings

Water dissociation barrier reduced by up to 37% due to clustering.

Helium suppresses water cluster formation and dissociation.

Control over water dissociation rates in MOF-74 achieved.

Abstract

We show that the water dissociation reaction H$_2$O$\rightarrow$OH+H in the confined environment of MOF-74 channels can be precisely controlled by the addition of the noble gas He. Elucidating the entire reaction process with ab initio methods and infrared (IR) spectroscopy, we prove that the interaction between water molecules is critical to the formation of water clusters, which reduce the dissociation barrier by up to 37% and thus influence the reaction significantly. Our time-resolved IR measurements confirm that the formation of these clusters can be suppressed by introducing He gas, providing unprecedented control over water dissociation rates. Since the water dissociation reaction is the cause of the structural instability of MOF-74 in the presence of water, our finding of the reaction mechanism lays the groundwork for designing water stable versions of MOF-74 as well as understanding water related phenomena in MOFs in general.