Experimental and theoretical approaches to understanding selective gas adsorption in metal-organic frameworks

Porous solids such as metal-organic frameworks (MOFs) are considered promising candidates for many industrial gas-separation applications, especially due to their structural and chemical versatility with respect to traditional solid sorbents such as zeolites. Rational tuning of such materials for improved performance requires that the interactions between the host framework and guest molecules be well-understood at the atomic level. Our research targets this detailed understanding of framework-guest systems using in situ and operando neutron scattering experiments, in which structure and dynamics are probed as a function of guest loading and temperature, along with comprehensive atomistic density functional theory-based (DFT) calculations from which various physical and dynamical properties can be extracted. We are currently investigating several MOFs which display interesting sorption behaviours, such as shape-dependent binding, "reverse sieving" (i.e. selectively absorbing larger gas molecules while rejecting smaller ones), and guest-responsive negative thermal expansion (NTE). This talk describes the suite of conventional and unconventional tools we have used to explore the structural and dynamic properties of these frameworks, yielding highly detailed information about their behaviour. Many of these methods can also be applied to a wide variety of systems involving host-guest interactions.