Fig. 2: Self-assembly of ZIF-8 particles and dimension control.
From: Low-dimensional assemblies of metal-organic framework particles and mutually coordinated anisotropy
a, b Quasi-3D superstructures assembled from 0.9-µm ZIF-8 RD particles on a rough substrate. For each particle, the coordination number n = 12. Large-view optical microscope image of the assembled crystals with a face-centered cubic structure (FCC) is shown in (a). Cartoons, zoomed-in optical images and SEMs in (b) show (100)-, (111)-, and (110)-oriented colloidal crystals; the axial angles are labeled. c–f 1D chains (n = 2) by assembling ZIF-8 RD (c–e) or truncated rhombic dodecahedra (TRD) (f) particles on a smooth substrate. Reflected-light confocal microscopy image in (c) reveals the well-arrayed rhombic faces (inset, orange dashed lines) within the RD chain. Cartoon in (d) illustrates that the particles stand on the substrate by their (110) faces and contact with one another by virtual patches (purple) to form a chain. Cartoon and SEM image in (e) show the top view of a colloidal chain. f Cartoon and bright-field optical image of chains assembled by TRD particles. g–j 2D chain bundles (n = 2~6). Optical (g) and SEM images (h) show the structure of ZIF-8 chain bundles and highlight the crosslinker particles (in blue). Cartoons in (i) illustrate the binding and the corresponding particle facets (purple) between the chains (at bottom layer) and the crosslinkers (at upper layer). A gap with a width of δ is observed between the bridged chains of TRD particles. Optical images in (j) show the flexible and rigid chain bundles according to the number density of crosslinkers. Color of chain segment denotes the deviation in angles from straight chain (white line). Scale bars: 5 µm for microscope images in (a, b), 2 μm for SEMs in (b), 5 and 2 µm (inset) for (c), 1 µm for (e, h), 10 µm for (f), 10 and 5 µm (inset) for (g), and 3 µm for (j).
