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.