Investigating the melting behaviour of polymorphic zeolitic imidazolate frameworks

Abstract

The study of polymorphic zeolitic imidazolate frameworks demonstrates the influence of linker chemistry and framework structure on their thermal behaviour.

The reactivity of an inorganic glass melt with ZIF-8

“…This leaves differences which are intrinsic to the two frameworks, namely linker chemistry and framework topology, which have both been found to be key factors in determining framework stability. 36 More dense frameworks, for example, are reported as being more stable due to enhanced dispersion interactions between the linkers, 37 and so the instability of ZIF-8 relative to ZIF-62 could therefore be ascribed to its lower framework density. 22,38 The addition of a methyl group to the imidazole ring has also been shown by molecular dynamics simulations to have a substantial effect on the high-temperature dynamics around the Zn centre 39 and so will also have an effect on the linker reactivity.…”

Multivariate analysis of disorder in metal–organic frameworks

“…Namely, the melting of the crystalline zinc imidazolate framework (ZIF), TIF-4 [Zn(Im) 1.8 (mbIm) 0.2 , Im – imidazolate and mbIm – 5-methylbenzimidazolate], which occurs at c.a . 400 °C where it forms a liquid that we denote a TIF-4 64 . Computational studies have suggested that the melting of ZIFs occurs on a picosecond timescale through the de-coordination of a linker followed by subsequent re-coordination of another linker in its place 65 .…”

Glassy behaviour of mechanically amorphised ZIF-62 isomorphs

“…This is important as the free space available in the pores of the materials may affect the steric freedom of the linkers, and therefore influence T g . 23 Both materials showed almost identical isotherms, with a maximum CO 2 uptake of 23.6 cm 3 g -1 in both cases. Further to this, the pore widths were determined to be 3.6 Å in both cases, and maximum pore volume of 0.043 cm 3 g -1 was found for a m [Zn(Im) 1.65 (bIm) 0.35 ] and a g [Zn(Im) 1.65 (bIm) 0.35 ].…”

“…2 The T g2 value for a g [Zn(Im) 1.0 (bIm) 1.0 ] represents by far the highest T g value ever measured for a ZIF glass, driven by its high bIm content. 23 To understand the production of a m ZIFs, an ex situ kinetics study on a m [Zn(Im) 1.65 (bIm) 0.35 ] formation was performed (Fig. S25- We note that crystalline ZIFs with the cag topology, such as ZIF-62 and ZIF-4, have 4 and 8-membered rings of ZnN 4 tetrahedra.…”