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1. Aperiodic metal–organic frameworks

   https://doi.org/10.1039/d0sc04798h  

   Oppenheim, Julius J. ; Skorupskii, Grigorii ; Dincă, Mircea ( October 2020 , Chemical Science)

   null (Ed.)

   Metal–organic frameworks (MOFs) represent one of the most diverse structural classes among solid state materials, yet few of them exhibit aperiodicity, or the existence of long-range order in the absence of translational symmetry. From this apparent conflict, a paradox has emerged: even though aperiodicity frequently arises in materials that contain the same bonding motifs as MOFs, aperiodic structures and MOFs appear to be nearly disjoint classes. In this perspective, we highlight a subset of the known aperiodic coordination polymers, including both incommensurate and quasicrystalline structures. We further comment upon possible reasons for the absence of such structures and propose routes to potentially access aperiodic MOFs. 

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2. Switching in Metal–Organic Frameworks

   https://doi.org/10.1002/anie.201900666  

   Bigdeli, Fahime ; Lollar, Christina T. ; Morsali, Ali ; Zhou, Hong‐Cai ( December 2019 , Angewandte Chemie International Edition)

   In recent years, metal–organic frameworks (MOFs) have become an area of intense research interest because of their adjustable pores and nearly limitless structural diversity deriving from the design of different organic linkers and metal structural building units (SBUs). Among the recent great challenges for scientists include switchable MOFs and their corresponding applications. Switchable MOFs are a type of smart material that undergo distinct, reversible, chemical changes in their structure upon exposure to external stimuli, yielding interesting technological applicability. Although the process of switching shares similarities with flexibility, very limited studies have been devoted specifically to switching, while a fairly large amount of research and a number of Reviews have covered flexibility in MOFs. This Review focuses on the properties and general design of switchable MOFs. The switching activity has been delineated based on the cause of the switching: light, spin crossover (SCO), redox, temperature, and wettability.

    

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3. Metal–Organic Frameworks with Low‐Valent Metal Nodes

   https://doi.org/10.1002/ange.202206353  

   Sikma, R. Eric ; Balto, Krista P. ; Figueroa, Joshua S. ; Cohen, Seth M. ( July 2022 , Angewandte Chemie)

   Metal–organic frameworks (MOFs) are crystalline, 2‐ and 3‐dimensional coordination polymers formed by bonding interactions between metals and multitopic organic ligands. These are typically formed using hard Lewis basic organic ligands with high oxidation state metal ions. The use of low‐valent metals as structural elements in MOFs is far less common, despite the widespread use of such metals for catalysis, luminescence, and other applications. This Minireview focuses on recent advances in the field of low‐valent MOFs and offers a perspective on the future development of these materials.

    

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4. Metal–Organic Frameworks with Low‐Valent Metal Nodes

   https://doi.org/10.1002/anie.202206353  

   Sikma, R. Eric ; Balto, Krista P. ; Figueroa, Joshua S. ; Cohen, Seth M. ( July 2022 , Angewandte Chemie International Edition)

   Metal–organic frameworks (MOFs) are crystalline, 2‐ and 3‐dimensional coordination polymers formed by bonding interactions between metals and multitopic organic ligands. These are typically formed using hard Lewis basic organic ligands with high oxidation state metal ions. The use of low‐valent metals as structural elements in MOFs is far less common, despite the widespread use of such metals for catalysis, luminescence, and other applications. This Minireview focuses on recent advances in the field of low‐valent MOFs and offers a perspective on the future development of these materials.

    

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5. Flux melting of metal–organic frameworks

   Longley, Louis ; Collins, Sean M. ; Li, Shichun ; Smales, Glen J. ; Erucar, Ilknur ; Qiao, Ang ; Hou, Jingwei ; Doherty, Cara M. ; Thornton, Aaron W. ; Hill, Anita J. ; et al ( March 2019 , Chemical science)

   Recent demonstrations of melting in the metal–organic framework (MOF) family have created interest in the interfacial domain between inorganic glasses and amorphous organic polymers. The chemical and physical behaviour of porous hybrid liquids and glasses is of particular interest, though opportunities are limited by the inaccessible melting temperatures of many MOFs. Here, we show that the processing technique of flux melting, ‘borrowed’ from the inorganic domain, may be applied in order to melt ZIF-8, a material which does not possess an accessible liquid state in the pure form. Effectively, we employ the high-temperature liquid state of one MOF as a solvent for a secondary, non-melting MOF component. Differential scanning calorimetry, small- and wide-angle X-ray scattering, electron microscopy and X-ray total scattering techniques are used to show the flux melting of the crystalline component within the liquid. Gas adsorption and positron annihilation lifetime spectroscopy measurements show that this results in enhanced, accessible porosity to a range of guest molecules in the resultant flux melted MOF glass. 

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