Facet‐Dependent Water Clustering in ZIF‐8 Enables High‐Efficiency Methane Storage

ABSTRACT Achieving high volumetric capacity for solid‐state methane (CH 4 ) storage under mild conditions remains a challenge for vehicular applications. While metal‐organic frameworks (MOFs) demonstrate excellent CH 4 physisorption kinetics, most fail to meet the U.S. Department of Energy (DOE)'s target of 263 v/v at pressures below 6.5 MPa. Here, we propose a strategy that engineers the exposed crystal facet of MOF to promote the clathrate formation on the surface, achieving an efficient combination of MOF adsorption and clathrate CH 4 storage. We find that the exposed {100} facets of cubic ZIF‐8 can induce polar water molecules to assemble into structured clusters and further encapsulate CH 4 molecules, attributed to electrostatic interactions and the van der Waals effect. Finally, the cubic ZIF‐8 boosts the massive generation of CH 4 clathrate on the exposed facets and maintains the physical adsorption capacity for CH 4 within the pores. In the fixed‐bed system, pre‐wetted cubic ZIF‐8 can efficiently store CH 4 with a recorded capacity of 343 v/v at 5 MPa, surpassing the DOE's target.