Using Hansen solubility parameters to study the encapsulation of caffeine in MOFs.

Hansen solubility parameters (HSP) have found their greatest use in the evaluation of solvent-polymer chemical interactions. Given their great interest among the scientific community, host-guest interactions in metal-organic frameworks (MOFs), with organic and inorganic moieties, could benefit from a HSP approach. In this work we have initiated the application of HSP to the study of caffeine encapsulation in MOFs ZIF-8 and NH2-MIL-88B(Fe). However, the availability of HSP for MOFs is nearly zero. As a first step to evaluating the potential of HSP for rational design we have made the simplifying assumption that the HSP distance of the caffeine-ligand interaction (i.e. ignoring the metal and the MOF structure) dominates the ability to form a MOF host-guest system. Although much work remains to be done, the first indications are that this approach has much potential.