Tao Lei, Khramenkova Elena, Lee Insu, Ikuno Takaaki, Khare Rachit, Jentys Andreas, Fulton John L, Kolganov Alexander A, Pidko Evgeny A, Sanchez-Sanchez Maricruz, Lercher Johannes A
Department of Chemistry and Catalysis Research Center, Technische Universität München, Lichtenbergstraße 4, 85748 Garching, Germany.
Inorganic Systems Engineering (ISE), Department of Chemical Engineering, Delft University of Technology, 2629 HZ Delft, The Netherlands.
J Am Chem Soc. 2023 Aug 16;145(32):17710-17719. doi: 10.1021/jacs.3c04328. Epub 2023 Aug 7.
The stoichiometric conversion of methane to methanol by Cu-exchanged zeolites can be brought to highest yields by the presence of extraframework Al and high CH chemical potentials. Combining theory and experiments, the differences in chemical reactivity of monometallic Cu-oxo and bimetallic Cu-Al-oxo nanoclusters stabilized in zeolite mordenite (MOR) are investigated. Cu-L edge X-ray absorption near-edge structure (XANES), infrared (IR), and ultraviolet-visible (UV-vis) spectroscopies, in combination with CH oxidation activity tests, support the presence of two types of active clusters in MOR and allow quantification of the relative proportions of each type in dependence of the Cu concentration. molecular dynamics (MD) calculations and thermodynamic analyses indicate that the superior performance of materials enriched in Cu-Al-oxo clusters is related to the activity of two μ-oxo bridges in the cluster. Replacing HO with ethanol in the product extraction step led to the formation of ethyl methyl ether, expanding this way the applicability of these materials for the activation and functionalization of CH. We show that competition between different ion-exchanged metal-oxo structures during the synthesis of Cu-exchanged zeolites determines the formation of active species, and this provides guidelines for the synthesis of highly active materials for CH activation and functionalization.
通过铜交换沸石将甲烷化学计量转化为甲醇，可在存在骨架外铝和高CH化学势的情况下实现最高产率。结合理论与实验，研究了稳定在丝光沸石（MOR）中的单金属铜氧和双金属铜铝氧纳米团簇的化学反应性差异。铜L边X射线吸收近边结构（XANES）、红外（IR）和紫外可见（UV-vis）光谱，结合CH氧化活性测试，支持MOR中存在两种活性团簇，并能根据铜浓度对每种类型的相对比例进行定量。分子动力学（MD）计算和热力学分析表明，富含铜铝氧团簇的材料的优异性能与团簇中两个μ-氧桥的活性有关。在产物萃取步骤中用乙醇替代HO导致形成乙基甲基醚，从而扩大了这些材料在CH活化和功能化方面的适用性。我们表明，在铜交换沸石合成过程中不同离子交换金属氧结构之间的竞争决定了活性物种的形成，这为合成用于CH活化和功能化的高活性材料提供了指导。
