Exploiting in situ NMR to monitor the formation of a metal-organic framework

The formation processes of metal-organic frameworks are becoming more widely researched using in situ techniques, although there remains a scarcity of NMR studies in this field. In this work, the synthesis of framework MFM-500(Ni) has been investigated using an in situ NMR strategy that provides information on the time-evolution of the reaction and crystallization process. In our in situ NMR study of MFM-500(Ni) formation, liquid-phase H-1 NMR data recorded as a function of time at fixed temperatures (between 60 and 100 degrees C) afford qualitative information on the solution-phase processes and quantitative information on the kinetics of crystallization, allowing the activation energies for nucleation (61.4 +/- 9.7 kJ mol(-1)) and growth (72.9 +/- 8.6 kJ mol(-1)) to be determined. Ex situ small-angle X-ray scattering studies (at 80 degrees C) provide complementary nanoscale information on the rapid self-assembly prior to MOF crystallization and in situ powder X-ray diffraction confirms that the only crystalline phase present during the reaction (at 90 degrees C) is phase-pure MFM-500(Ni). This work demonstrates that in situ NMR experiments can shed new light on MOF synthesis, opening up the technique to provide better understanding of how MOFs are formed.

Automated summary

In situ NMR studies on the formation of MFM-500(Ni) provide insights into the solution-phase processes and kinetics of crystallization, revealing activation energies for nucleation and growth. Complementary nanoscale information on rapid self-assembly prior to MOF crystallization is obtained through ex situ small-angle X-ray scattering, while in situ powder X-ray diffraction confirms the presence of phase-pure MFM-500(Ni) during the reaction. This work demonstrates the potential of in situ NMR experiments in shedding new light on MOF synthesis.