Recent reports of externally triggered,
controlled adsorption of
carbon dioxide (CO<sub>2</sub>) have raised the prospects of using
stimuli responsive metal–organic frameworks (MOFs) for energy
efficient gas storage and release. Motivated by these reports, here
we investigate CO<sub>2</sub> adsorption mechanisms in photoresponsive
PCN-123 and azo-IRMOF-10 frameworks. Using a combination of grand
canonical Monte Carlo and first-principles quantum mechanical simulations,
we find that the CO<sub>2</sub> adsorption in both frameworks is substantially
reduced upon light-induced isomerization of azobenzene, which is in
agreement with the experimental measurements. We show that the observed
behavior originates from inherently weaker interactions of CO<sub>2</sub> molecules with the frameworks when azobenzene groups are
in cis state rather than due to any steric effects that dramatically
alter the adsorption configurations. Our studies suggest that even
small changes in local environment triggered by external stimuli can
provide a control over the stimuli responsive gas adsorption and release
in MOFs
