No abstract

The modular nature of metal−organic frameworks (MOFs) leads to a very large number of possible structures. Highthroughput computational screening has led to a rapid increase in property data that has enabled several potential applications for MOFs, including gas storage, separations, catalysis, and other fields. Despite their rich chemistry, MOFs are typically named using an ad hoc approach, which can impede their searchability and the discovery of broad insights. In this article, we develop two systematic MOF identifiers, coined MOFid and MOFkey, and algorithms for deconstructing MOFs into their building blocks and underlying topological network. We review existing cheminformatics formats for small molecules and address the challenges of adapting them to periodic crystal structures. Our algorithms are distributed as open-source software, and we apply them here to extract insights from several MOF databases. Through the process of designing MOFid and MOFkey, we provide a perspective on opportunities for the community to facilitate data reuse, improve searchability, and rapidly apply cheminformatics analyses.

The isostructural, two-dimensional metal-organic frameworks (HNMe)M(Cldhbq) (M = Ti, V; Cldhbq = deprotonated 2,5-dichloro-3,6-dihydroxybenzoquinone) and (HNMe)Cr(dhbq) (dhbq = deprotonated 2,5-dihydroxybenzoquinone) are synthesized and investigated by spectroscopic, magnetic, and electrochemical methods. The three frameworks exhibit substantial differences in their electronic structures, and the bulk electronic conductivities of these phases correlate with the extent of delocalization observed via UV-vis-NIR and IR spectroscopies. Notably, substantial metal-ligand covalency in the vanadium phase results in the quenching of ligand-based spins, the observation of simultaneous metal- and ligand-based redox processes, and a high electronic conductivity of 0.45 S/cm. A molecular orbital analysis of these materials and a previously reported iron congener suggests that the differences in conductivity can be explained by correlating the metal-ligand energy alignment with the energy of intervalence charge-transfer transitions, which should determine the barrier to charge hopping in the mixed-valence frameworks.

Lithium‐ion batteries have remained a state‐of‐the‐art electrochemical energy storage technology for decades now, but their energy densities are limited by electrode materials and conventional liquid electrolytes can pose significant safety concerns. Lithium metal batteries featuring Li metal anodes, solid polymer electrolytes, and high‐voltage cathodes represent promising candidates for next‐generation devices exhibiting improved power and safety, but such solid polymer electrolytes generally do not exhibit the required excellent electrochemical properties and thermal stability in tandem. Here, an interpenetrating network polymer with weakly coordinating anion nodes that functions as a high‐performing single‐ion conducting electrolyte in the presence of minimal plasticizer, with a wide electrochemical stability window, a high room‐temperature conductivity of 1.5 × 10−4 S cm−1, and exceptional selectivity for Li‐ion conduction (tLi+ = 0.95) is reported. Importantly, this material is also flame retardant and highly stable in contact with lithium metal. Significantly, a lithium metal battery prototype containing this quasi‐solid electrolyte is shown to outperform a conventional battery featuring a polymer electrolyte.

Two iron–semiquinoid framework materials, (H2NMe2)2Fe2(Cl2 dhbq)3 (1) and (H2NMe2)4Fe3(Cl2 dhbq)3(SO4)2 (Cl2 dhbq n– = deprotonated 2,5-dichloro-3,6-dihydroxybenzoquinone) (2-SO 4 ), are shown to possess electrochemical capacities of up to 195 mAh/g. Employing a variety of spectroscopic methods, we demonstrate that these exceptional capacities arise from a combination of metal- and ligand-centered redox processes, a result supported by electronic structure calculations. Importantly, similar capacities are not observed in isostructural frameworks containing redox-inactive metal ions, highlighting the importance of energy alignment between metal and ligand orbitals to achieve high capacities at high potentials in these materials. Prototype lithium-ion devices constructed using 1 as a cathode demonstrate reasonable capacity retention over 50 cycles, with a peak specific energy of 533 Wh/kg, representing the highest value yet reported for a metal–organic framework. In contrast, the capacities of devices using 2-SO 4 as a cathode rapidly diminish over several cycles due to the low electronic conductivity of the material, illustrating the nonviability of insulating frameworks as cathode materials. Finally, 1 is further demonstrated to access similar capacities as a sodium-ion or potassium-ion cathode. Together, these results demonstrate the feasibility and versatility of metal–organic frameworks as energy storage materials for a wide range of battery chemistries.

No abstract

Materials that combine magnetic order with other desirable physical attributes could find transformative applications in spintronics, quantum sensing, low-density magnets, and gas separations. Among potential multifunctional magnetic materials, metal-organic frameworks in particular bear structures that offer intrinsic porosity, vast chemical and structural programmability, and tunability of electronic properties. Nevertheless, magnetic order within metal-organic frameworks has generally been limited to low temperatures, owing largely to challenges in creating strong magnetic exchange. Here, we employ the phenomenon of itinerant ferromagnetism to realize magnetic ordering at TC = 225 K in a mixed-valence chromium(II/III) triazolate compound, representing the highest ferromagnetic ordering temperature yet observed in a metal-organic framework. The itinerant ferromagnetism proceeds via a double-exchange mechanism, resulting in a barrierless charge transport below TC and a large negative magnetoresistance of 23% at 5 K.These observations suggest applications for double-exchange-based coordination solids in the emergent fields of magnetoelectrics and spintronics.

CrSBr is an air-stable two-dimensional (2D) van der Waals semiconducting magnet with great technological promise, but its atomic-scale magnetic interactions-crucial information for high-frequency switching-are poorly understood. An experimental study is presented to determine the CrSBr magnetic exchange Hamiltonian and bulk magnon spectrum. The A-type antiferromagnetic order using single crystal neutron diffraction is confirmed here. The magnon dispersions are also measured using inelastic neutron scattering and rigorously fit the excitation modes to a spin wave model. The magnon spectrum is well described by an intra-plane ferromagnetic Heisenberg exchange model with seven nearest in-plane exchanges. This fitted exchange Hamiltonian enables theoretical predictions of CrSBr behavior: as one example, the fitted Hamiltonian is used to predict the presence of chiral magnon edge modes with a spin-orbit enhanced CrSBr heterostructure.