Multifunctional Roles of Clathrate Hydrates 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 find that the stacked H2O nanocages in CHs assist to initialize CO2R by increasing the electron-binding ability of CO2. The substantial CO2R processes are further influenced by the hydrogen bond (H-bond) networks in CHs. The first intermediate CO2- in this process can be stabilized through cage structure reorganization into the H-bonded [CO2-···H-OHcage] complex. Further cooperative structural dynamics enables the complex to convert into a vital transient [CO22-···H-OHcage] intermediate via a low-barrier disproportionation-like process. Such a highly reactive intermediate spontaneously triggers sequent double proton transfer along its tethering H-bonds, finally converting it into HCOOH. These hydrogen-bonded nanoreactors feature multifunction in facilitating CO2R such as confining, tethering, H-bond catalyzing and proton pump. Our findings have a general interest and extend the knowledge of CO2R into porous aqueous systems.