Understanding polymorphism in metal-organic frameworks (MOFs) provides opportunities to unravel the process of MOF crystallization, and it enables the elucidation of structure-property relationships of compositionally identical crystals. Here, we present the modulator- and temperature-mediated polymorphic transformation of the kinetic product from Zr6-based MOF synthesis, EHU-30, to the thermodynamic product, UiO-66. The partial dissolution-recrystallization process was demonstrated by a combination of in situ powder X-ray diffraction (PXRD) and in situ 1H NMR spectroscopy where EHU-30 was heated in the presence of a monotopic acid modulator, acetic acid. Density functional theory (DFT) calculations show that the EHU-30 polymorph is less stable because the bent linkers have higher Gibbs free energy compared to linear linkers in the thermodynamic product, UiO-66.
Bibliographical noteFunding Information:
O.K.F. gratefully acknowledges support from the Defense Threat Reduction Agency (HDTRA1-19-1-0007). This research was supported in part by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2018R1A6A3A01011909). This work was also supported in part by the Yonsei University Research Fund (Yonsei Frontier Lab, Young Researcher Supporting Program) of 2018. PXRD and NMR studies made use of the IMSERC at Northwestern University, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205), the State of Illinois, and the International Institute for Nanotechnology (IIN); SEM study made use of EPIC facility of Northwestern University’s NU ANCE Center, which has received support from the SHyNE, the MRSEC program (NSF DMR-1720139) at the Materials Research Center, IIN, and the Keck Foundation. Computational works were performed using the High-Performance Computing cluster at the University of Oregon (Talapas), the Extreme Science and Engineering Discovery Environment (XSEDE) which is supported by National Science Foundation grant number ACI-1548562, and the Portland State University machine, Coeus, which is supported by the NSF (DMS1624776).
© 2020 American Chemical Society.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)
- Materials Science(all)
- Biomedical Engineering