Multifunctional Roles of Clathrate Hydrate Nanoreactors for CO Reduction.

In this study, we explore a possible platform for the CO reduction (CO R) in one of water's solid phases, namely clathrate hydrates (CHs), by ab initio molecular dynamics and well-tempered metadynamics simulations with periodic boundary conditions. We found that the stacked H O nanocages in CHs help to initialize CO R by increasing the electron-binding ability of CO . The substantial CO R processes are further influenced by the hydrogen bond networks in CHs. The first intermediate CO in this process can be stabilized through cage structure reorganization into the H-bonded [CO ⋅⋅⋅H-OH ] complex. Further cooperative structural dynamics enables the complex to convert into a vital transient [CO ⋅⋅⋅H-OH ] intermediate in a low-barrier disproportionation-like process. Such a highly reactive intermediate spontaneously triggers subsequent double proton transfer along its tethering H-bonds, finally converting it into HCOOH. These hydrogen-bonded nanoreactors feature multiple functions in facilitating CO R such as confining, tethering, H-bond catalyzing and proton pumping. Our findings have a general interest and extend the knowledge of CO R into porous aqueous systems.