Metal-Organic Frameworks Electrochemistry

Electrodeposition of Metal Organic Frameworks (MOF). Study of the influence of temperature and current parameters for Cu-BTC MOF deposition andinvestigation on the possibility to deposit other types of MOFs.status: publishe

Mg-MOF biodegradable coatings for drug delivery on Mg temporal implants

Metal organic frameworks (MOF’s) are novel materials designed for different applications with a growing interest in the last 10 years [1]. Horcajada et al. showed a drug delivery system based of MOF as drug nanocarriers, applying iron and 5 different organic linkers loading them with ibuprofen among other drugs [2]. Mg can also be used as the metal in the MOF structure (Mg-MOF), which has been successfully synthesised hydrothermally with DHTA (2,5-dihydroxyterephthalic acid) as organic linker and MgNO₃ as a metal source, in two different structures CPO-26-Mg and CPO-27-Mg [3]. Moreover, DHTA has shown a low toxicity in animal experiments, which makes it a biomaterial candidate [4]. In this study, Mg-MOF structures are electrochemically synthesized and deposited on pure Mg only using Mg from the substrate. This could be the first step in biodegradable drug delivery system to control the post-implantation inflamation of bioabsorbable Mg implant.status: publishe

Compatibility issues of yttria-stabilized zirconia solid oxide membrane in the direct electro-deoxidation of metal oxides

Direct electro‐deoxidation of metal oxides has become quite popular in the production of metals and alloys. In this process, metal oxide cathode is directly reduced to a metal in a molten CaCl2 salt bath. The anode material used is graphite. Over the years, graphite is reported to cause numerous process difficulties. Recently, based on the solid oxide membrane technology, yttria‐stabilized zirconia (YSZ) has been tested as oxygen ion conducting membrane for the anode. The success of using a membrane implies its long‐term stability in the bath. In this paper, it is seen that YSZ chemically degrades in a static melt of CaCl2 or CaCl2–CaO. The degradation occurs by leaching of yttria into solution leading to the formation of monoclinic zirconia which, being porous, reacts with the molten electrolyte to form calcium zirconate. However, on application of voltage, YSZ degrades via a different mechanism. The metallic calcium produced during electrolysis increases the electronic conductivity of the salt, apparently leading to the electrochemical reduction of zirconia to ZrO2−x. As a result, localized pores are formed which allow the infiltration of salts. Addition of yttria to the salt is seen to prevent both the chemical and electrochemical degradation of the membrane.status: publishe

Electron transfer-initiated epoxidation and isomerization chain reactions of beta-caryophyllene

The abundant sesquiterpene β-caryophyllene can be epoxidized by molecular oxygen in the absence of any catalyst. In polar aprotic solvents, the reaction proceeds smoothly with epoxide selectivities exceeding 70 %. A mechanistic study has been performed and the possible involvement of free radical, spin inversion, and electron transfer mechanisms is evaluated using experimental and computational methods. The experimental data-including a detailed reaction product analysis, studies on reaction parameters, solvent effects, additives and an electrochemical investigation-all support that the spontaneous epoxidation of β-caryophyllene constitutes a rare case of unsensitized electron transfer from an olefin to triplet oxygen under mild conditions (80 °C, 1 bar O2 ). As initiation of the oxygenation reaction, the formation of a caryophyllene-derived radical cation via electron transfer is proposed. This radical cation reacts with triplet oxygen to a dioxetane via a chain mechanism with chain lengths exceeding 100 under optimized conditions. The dioxetane then acts as an in situ-formed epoxidizing agent. Under nitrogen atmosphere, the presence of a one-electron acceptor leads to the selective isomerization of β-caryophyllene to isocaryophyllene. Observations indicate that this isomerization reaction is a novel and elegant synthetic pathway to isocaryophyllene.status: publishe

Stability of yttria stabilized zirconia membrane in molten CaCl₂-CaO melt

Yttria stabilized zirconia (YSZ), as an excellent oxygen ion conductor, is increasingly used as an oxygen ion membrane for the anode in the FFC Cambridge process. However, using a membrane implies that it exhibits long term stability in the bath. It has been reported that YSZ is stable chemically, but fails electrochemically in molten CaCl₂-CaO. In this work, we report, as opposed to previous reports, that YSZ is chemically not stable in molten CaCl₂-CaO melts. Electromigration only accelerates the instability. The degradation is seen to occur by leaching of yttria in solution leading to the formation of monoclinic zirconia which, being porous, reacts with the molten electrolyte to form calcium zirconate. We will also highlight possible countermeasures.status: publishe

Metal-organic framework deposition on dealloyed substrates

The functionalization of surfaces to obtain high specific surface areas is important for catalysis, energy storage and sensing. The two main approaches to obtain porous surfaces are the deposition of porous materials, like Metal–Organic Frameworks (MOFs), and the modification of substrates, for example by dealloying. MOF layers have higher specific surface areas than dealloyed structures, but they are easily damaged by external forces. In this work, we report on the combination of dealloying and MOF deposition. The functionalised surfaces have a much higher specific surface area (circa 7000 m2 m-2) than the simple sum of the specific area of a MOF layer and a dealloyed one. Moreover, the MOF crystals are protected by the dealloyed structures and are not easily removed by an external force. The presence of the metal scaffold may also enable fast heat exchange with the MOF, which is important for the use of these structures in e.g. adsorption rotors.crosscheck: This document is CrossCheck deposited related_data: Supplementary Information copyright_licence: The Royal Society of Chemistry has an exclusive publication licence for this journal copyright_licence: The accepted version of this article will be made freely available after a 12 month embargo period history: Received 21 March 2015; Accepted 14 August 2015; Accepted Manuscript published 14 August 2015; Advance Article published 3 September 2015; Version of Record published 29 September 2015status: publishe

Solvent-free synthesis of supported ZIF-8 films and patterns through transformation of deposited zinc oxide precursors

Film processing and patterning techniques are a prerequisite to fully exploit the potential of metal-organic frameworks (MOFs) in integrated applications. We report a solvent-free approach for the synthesis of ZIF-8 thin films and patterns through the reaction of ZnO films with melted 2-methylimidazole. © 2013 The Royal Society of Chemistry.status: publishe

Luminescent terbium-containing metal–organic framework films: new approaches for the electrochemical synthesis and application as detectors for explosives

The flexibility of the electrochemical synthesis of MOFs films is illustrated by the preparation of well-adhering layers of luminescent MOFs on electrically conductive solid substrates. The luminescent layers have been successfully tested for the detection of 2,4-dinitrotoluene (DNT).crosscheck: This document is CrossCheck deposited related_data: Supplementary Information identifier: Ernesto Rezende Souza (ResearcherID) copyright_licence: The Royal Society of Chemistry has an exclusive publication licence for this journal copyright_licence: The accepted version of this article will be made freely available after a 12 month embargo period history: Received 24 July 2014; Accepted 2 September 2014; Accepted Manuscript published 2 September 2014; Advance Article published 8 September 2014; Version of Record published 18 September 2014status: publishe

On controlling the anodic electrochemical film deposition of HKUST-1 metal-organic frameworks

© 2016 Elsevier Inc. All rights reserved. Anodic electrochemical synthesis presents itself as a powerful and rapid method to produce porous metal-organic framework (MOF) powders and deposit MOF films onto metal surfaces. Such layers are of interest for adsorptive, catalytic or sensor applications. However, electrochemical MOF synthesis is still in a preliminary stage while a need to better control the process and understand the influences of the process parameters emerges. This work focuses on controlling the deposition of copper-1,3,5-benzenetricarboxylate (HKUST-1, Cu-BTC) MOF layers and targeting different crystal sizes. Moreover, it aims to shed some light on the mechanisms underlying these changes. A number of strategies can be adopted to control the process and adjust the obtained crystal size. By adjusting the synthesis time or water content, the average crystal size can be controlled up to ∼10 μm for ethanol-based synthesis mixtures. The potential also has a pronounced effect, yet a suitable operation window must first be determined to avoid incomplete film formation or excessive film detachment. Furthermore, the influence of the solvent composition on the deposited film morphologies was investigated for mixtures of water, methanol, ethanol, 2-propanol, acetonitrile, N,N-dimethylformamide and dimethylsulfoxide.status: publishe

High pressure, high temperature electrochemical synthesis of metal-organic frameworks: films of MIL-100 (Fe) and HKUST-1 in different morphologies

Thanks to a new high temperature electrodeposition setup, MIL-100(Fe) is synthesized and deposited electrochemically for the first time. In comparison to other methods commonly used to produce this MOF, the reported synthesis allows formation of layers, and it takes place under milder conditions. The layers have been tested for anti-fouling, gas adsorption and vapor separation. With the same setup Cu–BTC MOF HKUST-1 has been deposited at different temperatures obtaining different morphologies.status: publishe