ResponZIF Structures: Zeolitic Imidazolate Frameworks as Stimuli-Responsive Materials

Abstract

Zeolitic imidazolate frameworks (ZIFs) have long been recognized as a prominent subset of the metal−organic framework (MOF) family, in part because of their ease of synthesis and good thermal and chemical stability, alongside attractive properties for diverse potential applications. Prototypical ZIFs like ZIF-8 have become embodiments of the significant promise held by porous coordination polymers as next-generation designer materials. At the same time, their intriguing property of experiencing significant structural changes upon the application of external stimuli such as temperature, mechanical pressure, guest adsorption, or electromagnetic fields, among others, has placed this family of MOFs squarely under the umbrella of stimuli-responsive materials. In this review, we provide an overview of the current understanding of the triggered structural and electronic responses observed in ZIFs (linker and bond dynamics, crystalline and amorphous phase changes, luminescence, etc.). We then describe the state-of-the-art experimental and computational methodology capable of shedding light on these complex phenomena, followed by a comprehensive summary of the stimuli-responsive nature of four prototypical ZIFs: ZIF-8, ZIF-7, ZIF-4, and ZIF-zni. We further expose the relevant challenges for the characterization and fundamental understanding of responsive ZIFs, including how to take advantage of their flexible properties for new application avenues.

Abstimmung des Hochdruckphasenverhaltens hochkomprimierbarer zeolithischer Imidazolatgerüstverbindungen: Vom diskontinuierlichen zum kontinuierlichen Porenverschluss durch Linkersubstitution

“…Als flexible MOF-Plattform wird die etablierte zeolithische Imidazolat-Gerüstverbindung ZIF-4 verwendet. [34][35][36][37][38] ZIF-4 besteht aus tetraedrisch koordinierten, zweiwertigen Metallkationen M 2 + (Zn 2 + oder Co 2 + ), die über die Stickstoffe von Imidazolat-Linkern (im À ) verbrückt sind (Abbildung 1a). ZIF-4 weist die chemische Zusammensetzung M(im) 2 auf und kristallisiert in einem zeolithartigen Netzwerk mit der cag-Topologie mit der Raumgruppe Pbca.…”

Recent advances in biomimetic soft robotics: fabrication approaches, driven strategies and applications

“…SRMs refer to the realization of perceivable and responsive materials to the external environment through the coordination of various functions in the materials, and there are usually many types of these materials. [216][217][218] Kim et al reviewed the SRMs used for soft robots from the perspective of different types of materials (including carbon nanomaterials, metal nanomaterials, shape memory polymers, liquid crystal polymers and elastomers, azobenzene, hydrogels, and bio-hybrids). 55 Ube et al reviewed photo mobile materials with crosslinked liquid-crystalline structures, which have great potential application value in microactuators and microfluidic devices.…”

Tuning the High‐Pressure Phase Behaviour of Highly Compressible Zeolitic Imidazolate Frameworks: From Discontinuous to Continuous Pore Closure by Linker Substitution

“…As a flexible MOF platform, we use the established zeolitic imidazolate framework ZIF-4. [34][35][36][37][38] ZIF-4 is composed of tetrahedrally coordinated divalent metal cations M 2 + (Zn 2 + or Co 2 + ) and imidazolate (im À ) linkers (Figure 1a), and it exhibits the chemical composition M(im) 2 and crystallizes in a zeolite-like network with the cag topology in the space group Pbca. Previous work revealed that the guest-free op phase of ZIF-4 transforms to a drastically contracted cp phase either when vacuum-cooled to temperatures below 140 K [33] or when hydrostatically compressed at pressures between 280 and 5000 bar, the latter depends on the pressure transmitting medium (PTM), the compression rate and the selected metal ion (Zn 2 + or Co 2 + ).…”