Fig. 2: Thermal analyses, in situ and ex situ synchrotron X-ray diffraction and scattering data.
a TGA (dotted lines, right vertical scale) and DSC (solid lines, left vertical scale) traces of ZIF-8 (left), ZIF-8-mim0.15im0.85 (middle) and agZIF-8-mim0.15im0.74bim0.11 (right, the grey shaded region highlights the integrated area for the determination of ∆Hm). The samples were cycled from 50 °C to 450 °C or 430 °C with a heating/cooling rate of ±10 °C min–1 twice. The insets show micrographs of ZIF-8, recrystallized ZIF-61-mim0.15im0.85, glassy agZIF-8-mim0.15im0.74bim0.11 derived by cooling the materials from 450 °C or 430 °C to room temperature. Contour maps of the VT-XRPD patterns are shown below the TGA/DSC data. Each map is generated from 11 XRPD patterns recorded at temperatures between 27 °C and 414 °C, containing 10 patterns recorded during heating and one additional pattern recorded after returning to room temperature. b–d VT-PDF data of ZIF-8 (b), ZIF-8-mim0.15im0.85 (c) and ZIF-8-mim0.15im0.74bim0.11 (d) derived from VT X-ray total scattering experiments. The insets highlight changes in the local structure (r < 10 Å, grey-shaded region). e Room temperature X-ray total scattering data in the form S(Q) of ZIF-8-mim0.15im0.74bim0.11 and agZIF-8-mim0.15im0.74bim0.11. The latter was prepared by melt-quenching from 430 °C in the DSC apparatus. f PDFs in the form D(r) obtained from the S(Q) data shown in (e). g Visualization of the relevant short-range atomic distances present in the ZIFs and their assignment to the peaks in the PDFs. Since mim–, im– and bim– are statistically distributed throughout the materials, the carbon atoms shown in cyan and orange are only partially occupied and thus have only a minor contribution to the PDFs.
