Fig. 2: Bulk structures of various MOFs.

HR-TEM images: a Isoreticular MOF-74 (IRMOF-74) (adapted with permission from ref. 56. © 2012 AAAS), b MOF-5 (adapted with permission from ref. 20. © 2017 Elsevier), and c PCN-333 (adapted with permission from ref. 58. © 2015 Springer Nature). The corresponding structural model is inset in each panel. The limited image resolution cannot reveal structural details other than the primary channels. d ADF-STEM image of MOF-74 processed by Fourier filtering, in which the triangular shape of the Zn clusters can be vaguely recognized, but individual Zn atomic columns cannot be resolved (adapted with permission from ref. 59. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim). e Low-dose HR-TEM image of ZIF-8 along the [111] zone axis: (left) the denoised raw image, in which the scale bars represent 2 nm; (right) symmetry-imposed, lattice-averaged image overlaid with a structural model of ZIF-8. In the processed image, Zn columns and two types of imidazole rings can be identified (adapted with permission from ref. 22. © 2017 Springer Nature). f Low-dose HR-TEM image of UiO-66 along the [011] zone axis processed by CTF-correction and the corresponding structural model. The high resolution of the image allows the benzene rings in the BDC linkers to be resolved, as indicated by the yellow arrows (adapted with permission from ref. 30. © 2018 AAAS).