Frustrated Flexibility in Metal-Organic Frameworks

Abstract

<div><div><div><p>Stimuli-responsive flexible metal-organic frameworks (MOFs) remain at the forefront of porous materials research due to their enormous potential for various technological applications. Here, we introduce the concept of frustrated flexibility in MOFs, which arises from an incompatibility of intra-framework dispersion forces with the geometrical constraints of the inorganic building units. Controlled by appropriate linker functionalization with dispersion energy donating alkoxy groups, this approach results in a series of MOFs exhibiting a new type of guest- and temperature-responsive structural flexibility characterized by reversible loss and recovery of crystalline order under full retention of framework connectivity and topology. The stimuli-dependent phase change of the frustrated MOFs involves non-correlated deformations of their inorganic building unit, as probed by a combination of global and local structure techniques together with computer simulations. Frustrated flexibility may be a common phenomenon in MOF structures, which are commonly regarded as rigid, and thus may be of crucial importance for the performance of these materials in various applications.</p></div></div></div>

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

“…B. durch Austausch von Metallionen oder durch Funktionalisierung des organischen Linkers [16] . Dies bietet die Möglichkeit, die Responsivität des Materials für eine bestimmte Anwendung anzupassen [4, 5, 13, 14, 17, 18] …”

“…[16] Dies bietet die Möglichkeit, die Responsivität des Materials für eine bestimmte Anwendung anzupassen. [4,5,13,14,17,18] Neben ihrer Ansprache auf die Adsorption von Gästen und die Temperatur hat die Ansprache flexibler MOFs auf mechanischen Druck zuletzt immer mehr Aufmerksamkeit erregt, nicht nur wegen ihrer Bedeutung für die Formung und Pelletierung von MOFs für Anwendungen in der Katalyse und Sorption, sondern auch für die Erforschung neuer Anwendungen, etwa als Stoßdämpfer. [19][20][21][22][23][24] Mehrere Derivate der Familie MIL-47/MIL-53 (MIL = Matériaux de l'Institut Lavoisier, M(X)(bdc); M = V 4 + , Cr 3 + , Al 3 + ; X = O 2À , OH À , F À ; bdc 2À = 1,4-Benzoldicarboxylat) [25] zeigen unter mechanischem Druck Phasenübergänge erster Ordnung von einer großporigen (large pore, lp) zu einer engporigen (narrow pore, np) Phase.…”

Mechanically interlocked molecules in metal–organic frameworks

“…The phase transition induced by a stimulus has also been applied to topologically rigid MOFs prepared with non-interlocked linkers. Such reticular systems show a breathing phenomenon of the pores, 120 converting, for example, insulator materials into conductor ones 121 or generating frustrated flexible hybrid MOFs, 122 among others. The development of the design of MIM-containing MOFs with reversible phase changes could be focused on these intriguing behaviours for obtaining flexible and functional dynamic MOFs.…”

Amorphous FeNiCu-MOFs as highly efficient electrocatalysts for the oxygen evolution reaction in an alkaline medium

“…Along with the fast development of MOFs, amorphous MOFs have been introduced recently, and they keep the basic building blocks without long-range crystallinity. 28,29 Amorphous catalysts have highly flexible structures due to their relatively loose permutation of atoms, which facilitates the pairing of active sites and arbitrary geometry. 30 Compared with crystalline MOFs, amorphous MOFs with a diverse morphology, substantial pores, more active sites, and higher conductivity could be applied to improve the electrocatalytic properties.…”