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

二氧化碳的活化生产高价值产品是催化领域的重要课题之一。在多相催化中，所有已知的工业CO2活化过程都需要高温和/或高压，实现CO2活化的有效多相催化剂几乎没有。在这个项目中，我们建议开发和优化一种ZnO催化剂，该催化剂将基于最近对单晶的观察，即二氧化碳通过形成三齿碳酸盐物种结合在ZnO（10-10）表面，因此可能对亲核加成非常活跃。我们项目的目的是首先将这项研究转移到ZnO粉末上，并研究金属沉积对CO2吸附的影响，已知在Cu和Au的情况下可以提高CO2的反应性。然后，我们将研究CO2吸附形成的碳酸盐物种与吸附的（亲核）分子之间是否可以诱导反应。下面的CO2和亲核分子的共吸附将启发催化结果。利用光致发光和EPR光谱对催化剂进行研究，以可靠地表征ZnO缺陷。2-甲基-3-丁醇-2-醇转化模型反应是ZnO碱度对CO2吸附的影响。利用红外（IR）光谱对氧化锌粉末进行研究，以表征其对CO2的吸附。将结果与单晶表面的相应IR-和eels结果进行比较，以精确识别单晶和氧化物颗粒表面上存在的不同化学物质。在工业应用方面，将研究相应的CO2活化反应，并利用工业固定床反应器优化其制造和金属装载。

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.