Abstract
Zeolite-related materials exhibit a range of novel properties and are of considerable interest for their potential engineering applications. Zeolitic imidazolate frameworks (ZIFs) display zeolite-type structures and are constructed by transitional metals and imidazole molecules.(1) With a wide variety of potential organic ligands, ZIFs present a new family of possible zeolite-related structures with tunable and functionalizable properties. Because of the coordinative metal–imidazolate bonding forming their frameworks, ZIFs are commonly more flexible than their aluminosilicate analogues. They also show unusual gas sorption capacity and related properties. Due to their framework flexibility, ZIFs can undergo structural transformations, e.g., during the sorption process(2) or under high temperature(3) or pressure.(4) It is of great significance to understand potential structural phase transitions since they strongly affect ZIFs’ structurally-related sorption and mechanical properties, which are essential to ZIFs-based technology innovations and industrial applications.Zeolite-related materials exhibit a range of novel properties and are of considerable interest for their potential engineering applications. Zeolitic imidazolate frameworks (ZIFs) display zeolite-type structures and are constructed by transitional metals and imidazole molecules.(1) With a wide variety of potential organic ligands, ZIFs present a new family of possible zeolite-related structures with tunable and functionalizable properties. Because of the coordinative metal–imidazolate bonding forming their frameworks, ZIFs are commonly more flexible than their aluminosilicate analogues. They also show unusual gas sorption capacity and related properties. Due to their framework flexibility, ZIFs can undergo structural transformations, e.g., during the sorption process(2) or under high temperature(3) or pressure.(4) It is of great significance to understand potential structural phase transitions since they strongly affect ZIFs’ structurally-related sorption and mechanical properties, which are essential to ZIFs-based technology innovations and industrial applications.
Highlights
Zeolitic imidazolate frameworks (ZIFs)-7 was synthesized based on the procedure given by Gücüyener et al.[6]
ZIF-7 was synthesized based on the procedure given by Gücüyener et al.[6]
Around 350 K, a phase transition was observed and found to be identical to the ZIF-7 lp to np phase transition reported by Aguado et al (Figure 1)
Summary
Communication increase with temperature of most of the vibrational modes. Such changes may reflect a structural rearrangement in the ZIF-. It seems reasonable that selective hydrolysis of Zn−N bonds in the ZIF-7 3D network structure leads to the formation of a more thermodynamically stable, dense phase, ZIF-7-III. Using cobalt(II) as the metal source, we obtained a new dense phase of ZIF-9 (ZIF-9-III) by the same mechanosynthesis method. This is the first systematic study of guestinduced phase transitions in ZIF-7. ZIF-7-III is the densest ZIF yet reported Incorporating this into ZIF-7’s phase transition triangle highlights the importance of guest molecule incorporation on the structural behavior of the ZIF family of materials. Analysis details, structure solution and refinement methods, and crystallographic data This material is available free of charge via the Internet at http://pubs.acs.org
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