Exceptional capture of methane at low pressure by an iron-based metal-organic framework.

The selective capture of methane (CH 4 ) at low concentrations and its separation from N 2 are extremely challenging owing to the weak host-guest interactions between CH 4 molecules and any sorbent material. Here, we report the exceptional adsorption of CH 4 at low pressure and the efficient separation of CH 4 /N 2 by MFM-300(Fe). MFM-300(Fe) shows a very high uptake for CH 4 of 0.85 mmol g -1 at 1 mbar and 298 K and a record CH 4 /N 2 selectivity of 45 for porous solids, representing a new benchmark for CH 4 capture and CH 4 /N 2 separation. The excellent separation of CH 4 /N 2 by MFM-300(Fe) has been confirmed by dynamic breakthrough experiments. In situ neutron powder diffraction, and solid-state nuclear magnetic resonance and diffuse reflectance infrared Fourier transform spectroscopies, coupled with modelling, reveal a unique and strong binding of CH 4 molecules involving Fe-OH⋯CH 4 and C⋯phenyl ring interactions within the pores of MFM-300(Fe), thus promoting the exceptional adsorption of CH 4 at low pressure.