Creation of new guest accessible space under gas pressure in a flexible MOF: multidimensional insight through combination of in situ techniques

Metal–organic frameworks (MOFs) are an important class of porous materials with numerous potential applications. Molecular level understanding of various processes involving MOFs is very important in order to design porous materials with improved properties. Here we describe the elucidation by means of single-crystal X-ray diffraction (SCD) of three different phases of Zn2(bdc)2(bpy) at different pressures of CO2. Moreover, this is a rare example where new space is created in the structure under gas pressure – space that was not previously occupied by guest molecules in any of the related structures. In addition to in situ SCD and sorption analysis, pressure-gradient differential scanning calorimetry (PG-DSC) provides very useful information about the system. This study represents the first instance where PG-DSC has been used to study the sorption behavior of a flexible porous framework.