Publications

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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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Today, carbon-rich fossil fuels, primarily oil, coal and natural gas, provide 85% of the energy consumed in the United States. The release of greenhouse gases from these fuels has spurred research into alternative, non-fossil energy sources. Lignocellulosic biomass is renewable resource that is carbon-neutral, and can provide a raw material for alternative transportation fuels. Plant-derived biomass contains cellulose, which is difficult to convert to monomeric sugars for production of fuels. The development of cost-effective and energy-efficient processes to transform the cellulosic content of biomass into fuels is hampered by significant roadblocks, including the lack of specifically developed energy crops, the difficulty in separating biomass components, the high costs of enzymatic deconstruction of biomass, and the inhibitory effect of fuels and processing byproducts on organisms responsible for producing fuels from biomass monomers. One of the main impediments to more widespread utilization of this important resource is the recalcitrance of cellulosic biomass and techniques that can be utilized to deconstruct cellulosic biomass.

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