Simulating Enhanced Methane Deliverable Capacity of Guest Responsive Pores in Intrinsically Flexible MOFs

A novel computational
procedure, based on the principles of flat-histogram
Monte Carlo, is developed for facile prediction of the adsorption
thermodynamics of intrinsically flexible adsorbents. We then demonstrate
how an accurate prediction of methane deliverable capacity in a metal–organic
framework (MOF) with significant intrinsic flexibility requires use
of such a method. Dynamic side chains in the framework respond to
methane adsorbates and reorganize to exhibit a more conducive pore
space at high adsorbate densities while simultaneously providing a
less conducive pore space at low adsorbate densities. This “responsive
pore” MOF achieves ∼20% higher deliverable capacity
than if the framework were rigid and elucidates a strategy for designing
high deliverable capacity MOFs in the future.