Activation of CO2 on ZnO surfaces and subsequent reactions with nucleophilic coadsorbates

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The activation of CO2 to produce high-value products is one of the most important topics in catalysis. In heterogeneous catalysis all the already known industrial processes of CO2 activation need high temperatures and/or pressures, effective heterogeneous catalysts to achieve the activation of CO2 are hardly available. In this project we propose to develop and optimize a ZnO catalyst which will be based on the recent observation made on single crystals that CO2 is bound to the ZnO (10-10) surface by formation of a tridentate carbonate species thus probably very reactive towards nucleophilic addition. The aim of our project is first to transpose this study to ZnO powders, and to examine the influence on CO2 adsorption of metal deposition, which is known in the case of Cu and Au to improve CO2 reactivity. Then, we will investigate whether a reaction can be induced between the carbonate species formed by CO2 adsorption and the (nucleophilic) molecules adsorbed. The following of the coadsorption of CO2 and of the nucleophilic molecules will enlighten the catalytic results. The catalysts will be investigated by photoluminescence and EPR spectroscopy to reliably characterize the ZnO defects. The influence of the ZnO basicity that may govern CO2 adsorption will be followed by 2-methyl-3-butyn-2-ol conversion model reaction. Studies using infrared (IR) spectroscopy on ZnO powders with and without metal (Cu, Au) deposits will be carried out to characterize CO2 adsorption. The results will be compared to the corresponding IR- and EELS-results obtained for the single crystalline surfaces to precisely identify the different chemical species present on the single crystal and on the oxide particle surfaces. With regard to an industrial application the corresponding CO2 activation reactions will be studied and their fabrication as well as their loading with metals will be optimized using industrialstyle fixed-bed reactors.