Metal–organic frameworks (MOFs) are often synthesized using various additives to modulate the crystallization. Here, we report the direct imaging of the crystal surface of MOF MIL-101 synthesized with different additives, using low-dose high-resolution transmission electron microscopy (HRTEM), and identify three distinct surface structures, at subunit cell resolution. We find that the mesoporous cages at the outermost surface of MIL-101 can be opened up by vacuum heating treatment at different temperatures, depending on the MIL-101 samples. We monitor the structural evolution of MIL-101 upon vacuum heating, using in situ X-ray diffraction, and find the results to be in good agreement with HRTEM observations, which leads us to speculate that additives have an influence not only on the surface structure but also on the stability of framework. In addition, we observe solid–solid phase transformation from MIL-101 to MIL-53 taking place in the sample synthesized with hydrofluoric acid.
|Original language||English (US)|
|Number of pages||8|
|Journal||Journal of the American Chemical Society|
|State||Published - Jul 19 2019|
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): FCC/1/1972-19
Acknowledgements: This research was supported by competitive center funds (FCC/1/1972-19) to Y.H. from King Abdullah University of Science and Technology (KAUST). X. Liu was supported by National Natural Science Foundation of China (No. 21771029, 11811530631 and 21573034). Y. Zhu acknowledges the financial support from the National Natural Science Foundation of China (Grant No. 21771161) and Thousand Talents Program for Distinguished Young Scholars. This research used the resources of KAUST’s Core Laboratories facilities.