ABSTRACT
The synthesis of MOF-74 (MOF = metal-organic framework) proceeds first through the generation of chemically and topologically distinct materials, referred to as phases, displaying exclusively carboxylate coordination, followed by further deprotonation to enable oxo coordination and MOF-74 formation. The synthesis of Mg-MOF-74 at high concentrations of linker and metal enables the stabilization and characterization of the previously unobserved, exclusively carboxylate coordinating phases. Ex situ and in situ approaches are leveraged to provide the time-resolved observation of Mg-MOF-74 synthesis and the formation of phases that precede Mg-MOF-74 formation as well as metastable phase dissolution. These data support dissolution and redeposition as the mechanism of MOF-74 formation and provide insight into the formation mechanism of MOFs with multiple linker coordination types.
Subject(s)
Metal-Organic Frameworks , Metal-Organic Frameworks/chemistry , Metals/chemistryABSTRACT
The spatial distribution of MOF functionalization reveals that postsynthetic modification (PSM)-derived microstructures can range from uniform to core-shell, affected by reagent reactivity and solvent choice. A suite of isocyanate reagents with varying reactivity were employed to study the effect of kinetics and experimental conditions on microstructure during PSM. Exploiting the difference in reactivity between chloroacetyl isocyanate and 4-bromophenyl isocyanate, a one-pot PSM reaction produces a dual-functionalized core-shell structure. Furthermore, a triple-functionalized Matryoshka structure is formed in a two-step PSM procedure using trifluoroacetyl isocyanate followed by a self-sorting reaction with chloroacetyl isocyanate and 4-bromophenyl isocyanate, demonstrating that a better understanding of the dynamics of PSM can support the design of MOFs with increasingly sophisticated architectures.
ABSTRACT
Metal-organic frameworks (MOFs) are generally synthesized in toxic formamide solvents. Greener solvents would lower production barriers and facilitate applications such as drug delivery. N,N-Diethyl-3-methylbenzamide (DEET), the most widely used insect repellent, is shown to serve this role. Furthermore, DEET-loaded MOFs can be leveraged in controlled-release insect repellent formulations.
ABSTRACT
Cyanuric triazide (CTA) and benzotrifuroxan (BTF) form a metal-free primary energetic cocrystal with suppressed volatility and improved thermal properties relative to CTA. Though electrostatic potential maps of the most stable conformations do not predict favorable interactions, a higher energy conformer has appropriate electrostatics and is selected by BTF in the cocrystal.
ABSTRACT
This paper describes the X-ray crystallographic structure of a derivative of the antibiotic teixobactin and shows that its supramolecular assembly through the formation of antiparallel ß-sheets creates binding sites for oxyanions. An active derivative of teixobactin containing lysine in place of allo-enduracididine assembles to form amyloid-like fibrils, which are observed through a thioflavin T fluorescence assay and by transmission electron microscopy. A homologue, bearing an N-methyl substituent, to attenuate fibril formation, and an iodine atom, to facilitate X-ray crystallographic phase determination, crystallizes as double helices of ß-sheets that bind sulfate anions. ß-Sheet dimers are key subunits of these assemblies, with the N-terminal methylammonium group of one monomer and the C-terminal macrocycle of the other monomer binding each anion. These observations suggest a working model for the mechanism of action of teixobactin, in which the antibiotic assembles and the assemblies bind lipid II and related bacterial cell wall precursors on the surface of Gram-positive bacteria.
