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 1H NMR data recorded as a function of time at fixed temperatures (between 60 and 100 °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 °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 °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.
Bibliographical noteFunding Information:
T. L. E. gratefully acknowledges the Royal Society for the award of a University Research Fellowship (6866). We thank Cardiff University and the EPSRC (grant reference EP/L504749/1) for funding. H. H.-M. Y. thanks the Samuel and Violette Glasstone Bequest for a Fellowship. We are grateful to the UK High-Field Solid-State NMR Facility for the award of spectrometer time. This facility was funded by EPSRC and BBSRC (contract reference PR140003), as well as the University of Warwick, including part funding through Birmingham Science City Advanced Materials Projects 1 and 2 supported by Advantage West Midlands and the European Regional Development Fund. The in situ powder XRD study on beamline I12 was supported by Diamond Light Source (beamtime EE16450). We thank Sebastian Henke, Roman Pallach, Niclas Heidenreich and Nghia Vo for assistance with in situ powder XRD measurements, and Dinu Iuga for assistance with NMR measurements.
© The Royal Society of Chemistry 2020.