Polymer-Coated Covalent Organic Frameworks as Porous Liquids for Gas Storage.

Several synthetic methods have recently emerged to develop high-surface-area solid-state organic framework-based materials into free-flowing liquids with permanent porosity. The fluidity of these porous liquid (PL) materials provides them with advantages in certain storage and transport processes. However, most framework-based materials necessitate the use of cryogenic temperatures to store weakly bound gases such as H, temperatures where PLs lose their fluidity.

Electrochemical and Structural Characterization of Soft Landed Tungsten-Substituted Lindqvist Polyoxovanadate-Alkoxides.

Lindqvist polyoxovanadate-alkoxide (POV-alkoxide) clusters are excellent candidates for applications in energy storage and conversion due to their rich electrochemical profiles. One approach to tune the redox properties of these cluster complexes is through substitutional cationic doping within the hexavanadate core. Here, we report the synthesis of a series of tungsten-substituted POV-alkoxide clusters with one and two tungsten atoms.

Atomically precise vanadium-oxide clusters.

Polyoxovanadate (POV) clusters are an important subclass of polyoxometalates with a broad range of molecular compositions and physicochemical properties. One relatively underdeveloped application of these polynuclear assemblies involves their use as atomically precise, homogenous molecular models for bulk metal oxides. Given the structural and electronic similarities of POVs and extended vanadium oxide materials, as well as the relative ease of modifying the homogenous congeners, investigation of the chemical and physical properties of pristine and modified cluster complexes presents a method toward understanding the influence of structural modifications ( crystal structure/phase, chemical makeup of surface ligands, elemental dopants) on the properties of extended solids.

Oxygen-atom vacancy formation and reactivity in polyoxovanadate clusters.

Reducible metal oxides (RMOs) are widely used materials in heterogeneous catalysis due to their ability to facilitate the conversion of energy-poor substrates to energy-rich chemical fuels and feedstocks. Theoretical investigations have modeled the role of RMOs in catalysis and found they traditionally follow a mechanism in which the generation of oxygen-atom vacancies is crucial for the high activity of these solid supports. However, limited spectroscopic techniques for in situ analysis renders the identification of the reactivity of individual oxygen-atom vacancies on RMOs challenging.

Physicochemical Factors That Influence the Deoxygenation of Oxyanions in Atomically Precise, Oxygen-Deficient Vanadium Oxide Assemblies.

Here, we report our findings related to the structural and electronic considerations that influence the rate of oxygen-atom transfer (OAT) to oxygen-deficient polyoxovanadate alkoxide (POV-alkoxide) clusters ([VO(OCH)]; = 1-, 0, 1+). A comparison of the reaction times required for the reduction of nitrogen-containing oxyanions (NO, = 2, 3) by the POV-ethoxide cluster in its anionic (; VV), neutral (; VVV), or cationic (; VVV) charge state reveals that OAT is significantly influenced by three factors: (1) ion-pairing interactions between the POV-alkoxide and the negatively charged oxyanion; (2) oxidation states of remote vanadyl ions in the Lindqvist assembly; (3) the steric bulk surrounding the coordinatively unsaturated V ion. This work provides atomic-level insight related to structure-function relationships that govern the rate of OAT at metal oxide surfaces using polyoxometalate clusters as molecular models.

Acid-Induced, Oxygen-Atom Defect Formation in Reduced Polyoxovanadate-Alkoxide Clusters.

Here, we present the first example of acid-induced, oxygen-atom abstraction from the surface of a polyoxometalate cluster. Generation of the oxygen-deficient vanadium oxide, [VO(OCH)], was confirmed via independent synthesis. Spectroscopic analysis using infrared and electronic absorption spectroscopies affords resolution of the electronic structure of the oxygen-deficient cluster (oxidation state distribution = [VV]).

Site-selective halogenation of mixed-valent vanadium oxide clusters.

Here, we expand on the synthesis and characterization of chloride-functionalized polyoxovanadate-alkoxide (POV-alkoxide) clusters, to include the halogenation of mixed-valent vanadium oxide assemblies. These findings build on our previously disclosed results describing the preparation of a mono-anionic chloride-functionalized cluster, [V6O6Cl(OC2H5)12]1-, by chlorination of [V6O7(OC2H5)12]2- with AlCl3, aimed at understanding the electronic consequences of the introduction of halide-defects in bulk metal oxides (e.g.

Electronic Consequences of Ligand Substitution at Heterometal Centers in Polyoxovanadium Clusters: Controlling the Redox Properties through Heterometal Coordination Number.

The rational control of the electrochemical properties of polyoxovanadate-alkoxide clusters is dependent on understanding the influence of various synthetic modifications on the overall redox processes of these systems. In this work, the electronic consequences of ligand substitution at the heteroion in a heterometal-functionalized cluster was examined. The redox properties of [V O (OCH ) FeCl] (1-[V FeCl]) and [V O (OCH ) Fe]X (2-[V Fe]X; X=ClO , OTf) were compared in order to assess the effects of changing the coordination environment around the iron center on the electrochemical properties of the cluster.

Oxygen atom transfer with organofunctionalized polyoxovanadium clusters: O-atom vacancy formation with tertiary phosphanes and deoxygenation of styrene oxide.

We report a rare example of oxygen atom transfer (OAT) from a polyoxometalate cluster to a series of tertiary phosphanes. Addition of PR (PR = PMe, PMePh, PMePh, PPh) to a neutral methoxide-bridged polyoxovanadate-alkoxide (POV-alkoxide) cluster, [VO(OMe)], results in isolation of a reduced structure with phosphine oxide datively coordinated to a site-differentiated V ion. A positive correlation between the steric and electronic properties of the phosphane and the reaction rate was observed.

Site-Selective Halogenation of Polyoxovanadate Clusters: Atomically Precise Models for Electronic Effects of Anion Doping in VO.

We report the synthesis and characterization of a monochloride-functionalized polyoxovanadate-alkoxide (POV-alkoxide) cluster, which can serve as a molecular model for halogen-doped vanadium oxide (VO) materials that have recently attracted great interest as advanced materials for energy-saving smart window applications. Chloride-substituted variants of the Lindqvist vanadium-oxide cluster were obtained via two distinct chemical pathways: (1) direct halogenation of the isovalent parent POV-alkoxide architecture, [VO(OCH)] with AlCl and (2) coordination of a chloride ion to a coordinatively unsaturated vanadium center within a cluster that bears a single oxygen-atom vacancy, [VO(OCH)]. Notably, our direct halogenation constitutes the first example of selective, single-site halide doping of homometallic metal oxide clusters.

Conversion of NO (x = 2, 3) to NO using an oxygen-deficient polyoxovanadate-alkoxide cluster.

We report the activation of nitrogen-containing oxyanions using an oxygen-deficient polyoxovanadate-alkoxide cluster. Reduction of NO and NO results in near-quantitative oxygen atom transfer to the coordinatively unsaturated V ion, and selective formation of NO. These results provide insight into possible mechanisms of oxyanion reduction by polyoxometalates.

Controlling Metal-to-Oxygen Ratios via M═O Bond Cleavage in Polyoxovanadate Alkoxide Clusters.

In this manuscript, we further investigate the use of Lindqvist polyoxovanadate alkoxide (POV-alkoxide) clusters as homogeneous molecular models of reducible metal oxides (RMO), focusing on the structural and electronic consequences of forming one or two oxygen-deficient sites. We demonstrate the reactivity of a POV-alkoxide cluster, [VO(OCH)], with a reductant, revealing routes for controlling metal-to-oxygen ratios in self-assembled polynuclear ensembles through post-synthetic modification. The outlook of this science is bolstered by the fact that, in both cases, O-atom removal reveals reduced V ions at the surface of the cluster.

Organic Functionalization of Polyoxovanadate-Alkoxide Clusters: Improving the Solubility of Multimetallic Charge Carriers for Nonaqueous Redox Flow Batteries.

The success of nonaqueous redox flow battery technology requires synthetic advances in charge carrier design to increase compatibility with organic solvents. Herein, previous discoveries related to the development of multimetallic charge carriers are built upon with the high-yielding syntheses of ether- functionalized polyoxovanadate-alkoxide clusters, [V O (OR) (OCH ) CR'] (R=CH , C H ; R'=CH , CH OCH , CH OC H OCH ). Like their homoleptic congeners [V O (OR) ] (R=CH , C H ), these clusters exhibit four redox events, spanning nearly a two-volt window, and demonstrate rapid electron-transfer kinetics.

Oxygen-Atom Vacancy Formation at Polyoxovanadate Clusters: Homogeneous Models for Reducible Metal Oxides.

We report the first example of oxygen-atom vacancy formation at the surface of a polyoxometalate, highlighting the ability of a polyoxovanadate-alkoxide cluster, [VO(OCH)], to function as a homogeneous model for reducible metal oxides. The removal of an oxide ion from [VO(OCH)] results in the formation of a reactive vanadium(III) cation within the multimetallic framework. Generation of [VO(OCH)] is confirmed by H NMR, infrared and electronic absorption spectroscopies, as well as electrospray ionization mass spectrometry.

[Traumatic pulmonary evisceration in a child. Apropos of 2 cases].

Two cases of pulmonary traumatic evisceration are reported. The question is about exceptional lesions very spectacular and good tolerated.