Unusual and Tunable Negative Linear Compressibility in the Metal–Organic Framework MFM-133(M) (M = Zr, Hf)

Abstract

High-pressure single-crystal X-ray structural analyses of isostructural MFM-133(M) (M = Zr, Hf) of flu topology and incorporating the tetracarboxylate ligand TCHB [HTCHB = 3,3',5,5'-tetrakis(4-carboxyphenyl)-2,2',4,4',6,6'-hexamethyl-1,1'-biphenyl] and {M(μ-OH)(OH)(COO)} clusters confirm negative linear compressibility (NLC) behavior along the c axis. This occurs via a three-dimensional wine-rack NLC mechanism leading to distortion of the octahedral cage toward a more elongated polyhedron under static compression. Despite the isomorphous nature of these two structures, MFM-133(Hf) shows a higher degree of NLC than the Zr(IV) analogue. Thus, for the first time, we demonstrate here that the NLC property can be effectively tuned in a framework material by simply varying the inorganic component of the frameworks without changing the network topology and structure.

A Flexible Interpenetrated Zirconium‐Based Metal–Organic Framework with High Affinity toward Ammonia

“…MOFs based on Zr 6 nodes are known for their outstanding thermal and chemical stability as well as diverse structures . Whereas the majority of Zr‐MOFs are rigid owing to the high connectivity of the Zr 6 nodes, some are reported to be flexible by employing nonrigid linkers or by reducing the connectivity of Zr 6 nodes, resulting in structural changes upon exposure to external stimuli such as guest molecules, temperature, and pressure . In our previous work, a flexible MOF (NU‐1400) comprising 4‐connected Zr 6 nodes and tetratopic linkers, was synthesized, and the framework presents different conformations and tunable accessibility to the Lewis‐acidic Zr IV sites induced by the guest molecules .…”

Metal–Organic Frameworks in Modern Physics: Highlights and Perspectives

“…[134,138] Scale bars, 1 µm. [149,152,153,157,[159][160][161]164] Reproduced with permission. [135] Copyright 2019, Springer Nature.…”

“…An intriguing finding is that the hierarchical MOF structure itself is similar to a metamaterial (see Figure illustrating results from refs. ), which is characterized by the different interactions (mechanical, electromagnetic) between the central element, a meta atom of a specific shape and size, with its neighbors . Metamaterials also demonstrate unconventional mechanical behavior.…”

“…Comparison of the structures of MOFs and metamaterials (MM) having similar unconventional mechanical properties as negative Poisson's ratio, negative linear compressibility, twisting under the pressure, and origami behavior that means an ability to lay the structure in one direction and inability in another (navy arrows indicate the stimuli, red and blue ones correspond to structural response). The MOF structures were extracted from CIF files . Reproduced with permission .…”

Anomalous Lattice Dynamics in AgC4N3: Insights From Inelastic Neutron Scattering and Density Functional Calculations

“…This type of abnormal behavior is known as negative linear or area compressibility (NLC or NAC). The behavior is basically observed in materials with highly anisotropic bonding and open framework type structures (Goodwin et al, 2008a ; Weng et al, 2008 ; Cairns et al, 2012 , 2013 ; Cairns and Goodwin, 2015 ; Wang et al, 2016 , 2017 ; Gupta et al, 2017 ; Zeng et al, 2017a , b ; Yan et al, 2018 ). The anisotropic character of elastic properties is a measure of the magnitude of NLC (or NAC) in a material.…”