Hypergolic materials, capable of spontaneous ignition upon contact with an external oxidizer, are of critical importance as fuels and propellants in aerospace applications (e.g., rockets and spacecraft). Currently used hypergolic fuels are highly energetic, toxic, and carcinogenic hydrazine derivatives, inspiring the search for cleaner and safer hypergols. Here, we demonstrate the first strategy to design hypergolic behavior within a metal-organic framework (MOF) platform, by using simple “trigger” functionalities to unlock the latent and generally not recognized energetic properties of zeolitic imidazolate frameworks, a popular class of MOFs. The herein presented six hypergolic MOFs, based on zinc, cobalt, and cadmium, illustrate a uniquely modular platform to develop hypergols free of highly energetic or carcinogenic components, in which varying the metal and linker components enables the modulation of ignition and combustion properties, resulting in excellent hypergolic response evident by ultrashort ignition delays as low as 2 ms.

We report the first systematic experimental and theoretical study of the relationship between the linker functionalization and the thermodynamic stability of metal–organic frameworks (MOFs) using a model set of eight isostructural zeolitic imidazolate frameworks (ZIFs) based on 2-substituted imidazolate linkers. The frameworks exhibit a significant (30 kJ·mol–1) variation in the enthalpy of formation depending on the choice of substituent, which is accompanied by only a small change in molar volume. These energetics were readily reproduced by density functional theory (DFT) calculations. We show that these variations in the enthalpy of MOF formation are in linear correlation to the readily accessible properties of the linker substituent, such as the Hammett σ-constant or electrostatic surface potential. These results provide the first quantifiable relationship between the MOF thermodynamics and the linker structure, suggesting a route to design and tune MOF stability.

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Supercritical carbon dioxide (CO 2 ) is an established medium for synthesizing molecular compounds and activation of microporous solids, but is much less explored for transformations of high-melting ionic reactants, such as metal oxides. We show that supercritical CO 2 enables direct, clean, and rapid transformation of zinc oxide into zeolitic imidazolate frameworks (ZIFs), without requiring toxic or corrosive metal nitrate or chloride precursors, organic or aqueous solvents, additives, or auxiliaries. While recent syntheses of coordination polymers and metal−organic frameworks from supercritical CO 2 highlighted the need for specialized metal reagents designed for solubility, we unexpectedly find that ZnO is quantitatively converted into grams of diverse ZIFs in minutes, with hundred grams of popular ZIF-8 accessible within an hour.

Metal-organic frameworks (MOFs) have emerged as highly versatile materials with applications in gas storage and separation, solar light energy harvesting and photocatalysis. The design of new MOFs, however, has been hampered by the lack of computational methods for ab initio MOF structure prediction, which could be used to inspire and direct experimental synthesis. Here, we report the first ab initio method for the prediction of MOF structures and test it against a diverse set of known MOFs that were chosen for their differences in topology, metal coordination geometry, and ligand binding sites. In all cases, our calculations produced structures that match experiment using only the target composition and ligand molecular structure, proving the versatility of our procedure. The herein presented methodology utilizes the point group symmetry of ligands to enable, for the first time, prediction of MOF structures from first principles, without having to resort to empirical guidelines based on rigid connectivity of nodes and linkers, or to previously determined crystal structures and topologies of known MOFs. This advance provides the first tool to change MOF design from an empirically based process that is based on chemistʼs intuition rooted in literature-or database-established knowledge of node-and-linker connectivity to a more general and theory-driven materials development. This ab initio MOF structure prediction approach, which is here validated on a range of known MOF classes, provides a unique opportunity to explore the phase landscape of MOFs computationally and enables MOF research and development even in case of limited access to laboratory resources, as for example in case of a global pandemic.