Hydrogen Bond Networks of Glycol Molecules on ZIF-8 Surfaces as Semipermeable Films for Efficient Carbon Capture

Efficient carbon capture is an essential step in many energy-related processes. Here, we use molecular dynamics simulations and free energy analysis to investigate the inherent implication of the ZIF-8/glycol slurry based adsorption and absorption hybrid technique for carbon capture. Our results reveal that the formation of two-layer ordered hydrogen bond (HB) networks of glycol molecules on the ZIF-8 surface is the physical origin of the high efficiency of using ZIF-8/glycol slurry for carbon capture. It is found that the film composed of two-layer HB networks acts as a selective gatekeeper, allowing the penetration of CO2 molecules but efficiently blocking CH4. The interaction between the HB-forming solvent and ZIF-8 is the key to the formation of the semipermeable film, while the solute-solvent interaction is essential for film crossing. Finally, we discuss the basis for the design of highly efficient nanopore/slurry system for filtering and separation technologies. The uncovered mechanism for the hybrid technique opens up an exciting strategy for highly efficient CO2 separation.