Multifunctional Roles of Clathrate Hydrate Nanoreactors for CO2 Reduction

In this study, we explore a possible platform for the CO2 reduction (CO2R) 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 H2O nanocages in CHs help to initialize CO2R by increasing the electron-binding ability of CO2. The substantial CO2R processes are further influenced by the hydrogen bond networks in CHs. The first intermediate CO2 in this process can be stabilized through cage structure reorganization into the H-bonded [CO2- center dot center dot center dot H-OHcage] complex. Further cooperative structural dynamics enables the complex to convert into a vital transient [CO22- center dot center dot center dot H-OHcage] 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 CO2R such as confining, tethering, H-bond catalyzing and proton pumping. Our findings have a general interest and extend the knowledge of CO2R into porous aqueous systems.