Electrospray Mass Spectrometry Investigation into the Formation of CPO-27

Electrospray ionization mass spectrometry (ESI-MS) has been utilized to investigate the self-assembly processes occurring during the formation of the microporous metal–organic framework CPO-27-M (M = Co, Ni). The mono- and dinuclear building units {M(Hxdhtp)} and {M2(Hxdhtp)}, where Hxdhtp is the organic linker HxC8O6 and fragments thereof, were identified as key species present in the reaction mixture during the product formation. Time-resolved powder X-ray diffraction analysis was used to follow the synthesis and confirmed that no other crystalline products occur in the reaction mixture prior to the crystallization of CPO-27-Ni. When equimolar reactions were performed at room temperature, compounds [(M(H2dhtp)(H2O)4·2H2O] (M = Co, Ni) crystallized instead of CPO-27 obtained at the higher temperature of the solvothermal procedure. It was confirmed that mono- and dinuclear species are key building blocks not only in the formation of CPO-27-M but also in the formation of the 1D chain structure (M(H2dhtp)(H2O)4) obtained from these room-temperature reactions.