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Kinetics and mechanism of metal-organic framework thin film growth: Systematic investigation of HKUST-1 deposition on QCM electrodes

Chemical Science

Stavila, Vitalie S.; Volponi, Joanne V.; Katzenmeyer, Aaron M.; Dixon, Matthew C.; Allendorf, Mark D.

We describe a systematic investigation of the factors controlling step-by-step growth of the metal-organic framework (MOF) [Cu 3(btc) 2(H 2O) 3]·xH 2O (also known as HKUST-1), using quartz crystal microbalance (QCM) electrodes as an in situ probe of the reaction kinetics and mechanism. Electrodes coated with silica, alumina and gold functionalized with OH- and COOH-terminated self-assembled monolayers (SAMs) were employed to determine the effects of surface properties on nucleation. Deposition rates were measured using the high sensitivity available from QCM-D (D = dissipation) techniques to determine rate constants in the early stage of the process. Films were characterized using grazing incidence XRD, SEM, AFM, profilometry and reflection-absorption IR spectroscopy. The effects of reaction time, concentration, temperature and substrate on the deposition rates, film crystallinity and surface morphology were evaluated. The initial growth step, in which the surface is exposed to copper ions (in the form of an ethanolic solution of copper(ii) acetate) is fast and independent of temperature, after which all subsequent steps are thermally activated over the temperature range 22-62 °C. Using these data, we propose a kinetic model for the Cu 3(btc) 2 growth on surfaces that includes rate constants for the individual steps. The magnitude of the activation energies, in particular the large entropy decrease, suggests an associative reaction with a tight transition state. The measured activation energies for the step-by-step MOF growth are an order of magnitude lower than the value previously reported for bulk Cu 3(btc) 2 crystals. Finally, the results of this investigation demonstrate that the QCM method is a powerful tool for quantitative, in situ monitoring of MOF growth in real time. © 2012 The Royal Society of Chemistry.

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TYPE Journal Article YEAR 2012
ScopusOSTI

MOF films for microsensor coatings

Materials Research Society Symposium Proceedings

Robinson, Alex L.; Allendorf, Mark D.; Stavila, Vitalie S.; Thornberg, Steven M.

Metal organic framework (MOF) materials are a class of hybrid organic-inorganic crystalline materials whose pore structures and chemical properties can be tailored by the selection of component chemical moieties. Many MOFs have extraordinary intrinsic surface areas, capable of adsorbing large quantities of other chemicals, such as volatile organic compounds or moisture. Upon absorption of guest molecules, many MOFs undergo reversible changes in the dimensions of their unit cells. These properties suggest several routes to chemical sensing in which the transduction mechanisms are: 1) the stress induced at an interface between a flexible MOF layer and a static microcantilever fabricated with a built-in piezoresistive stress sensor; 2) the change in the resonant frequency of an oscillating microcantilever induced by mass adsorption; and 3) the change in the resonant frequency of a acoustic sensor, such as a surface acoustic wave (SAW) sensor through changes in mass loading and film moduli. This paper focuses on humidity sensing by SAWs coated with Cu 3(BTC) 2 (HKUST-1) over a very broad concentration range. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. © 2011 Materials Research Society.

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TYPE Conference YEAR 2011
OSTIScopus
Results 176–200 of 216
Results 176–200 of 216