The Crystalline Sponge Method in Water

The crystalline sponge method allows for the elucidation of the (absolute) structure of molecules using single-crystal X-ray diffraction and eliminates the need for crystals of the target compound. An important limitation for the application of the crystalline sponge method is the instability of the available crystalline sponges that can act as host crystals, in most of the cases consisting of metal-organic framework (MOF) compounds. The MOF host crystal that is most often used decomposes in protic or nucleophilic solvents or when guest molecules with Lewis basic substituents are introduced. Here a class of stable MOF hosts based on f-block metals is disclosed, that are suitable for applying the crystalline sponge method to the aforementioned solvents and guest molecules. We show that these hosts not only increase the scope of the crystalline sponge method to a wider array of guests and solvents, but that they can even be applied to aqueous solutions containing hydrophilic guest molecules, thereby extending the crystalline sponge method to the important field of water-based chemistry.