An amide-functionalised metal organic framework
(MOF) material, MFM-136, shows a high CO2 uptake of
12.6 mmol g-1 at 20 bar and 298 K. MFM-136 is the first example
of acylamide pyrimidyl isophthalate MOF without
open metal sites, and thus provides a unique platform to
study guest binding, particularly the role of free amides.
Neutron diffraction reveals that, surprisingly, there is no
direct binding between the adsorbed CO2/CH4 molecules
and the pendant amide group in the pore. This observation
has been confirmed unambiguously by inelastic neutron
spectroscopy. This suggests that introduction of functional
groups solely may not necessarily induce specific guest-host
binding in porous materials, but it is a combination of pore
size, geometry, and functional group that leads to enhanced
gas adsorption properties.