Metal coordination and metal activation abilities of commonly unreactive chloromethanes toward metal–organic frameworks

Over the last two decades, metal-organic frameworks (MOFs) have received particular attention because of their attractive properties such as permanent nanoporosity and the extraordinary functionality of open coordination sites (OCSs) at metal nodes. In particular, MOFs with open-state OCSs have shown potential in applications such as chemical separation, molecular sorption, catalysis, ionic conduction, and sensing. Thus, the activation of OCSs, i.e., the removal of coordinated solvent to produce open-state OCSs, has been viewed as an essential step that must be performed prior to the use of the MOFs in the aforementioned applications. This Feature Article focuses on the chemical functions of the commonly unreactive chloromethanes, i.e., dichloromethane (DCM) and trichloromethane (TCM), including their coordination to OCSs and activation of OCSs. Treatment with a chloromethane is a chemical route to activate OCSs that does not require an additional supply of external thermal energy. Importantly, a plausible mechanism for the chemical process, in which DCM and TCM weakly coordinate to the OCSs and then spontaneously dissociate in an intermediate step, which is proposed based on the results obtained from Raman studies will be discussed. Possible applications of chloromethane treatment to activate large-area MOF films and MOF-polymer mixed matrices, which can be propagated in molecular capture, will also be described.