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通过原位电子顺磁共振和紫外/可见光谱揭示的铜/[氢氧化铜]对甲烷氧化及丝光沸石铜中的位点特异性动力学

Methane Oxidation over Cu /[CuOH] Pairs and Site-Specific Kinetics in Copper Mordenite Revealed by Operando Electron Paramagnetic Resonance and UV/Visible Spectroscopy.

作者信息

Fischer Jörg Wolfram Anselm, Brenig Andreas, Klose Daniel, van Bokhoven Jeroen Anton, Sushkevich Vitaly L, Jeschke Gunnar

机构信息

Institute for Molecular Physical Science, ETH Zurich, Vladimir-Prelog-Weg 1-5/10, 8093, Zurich, Switzerland.

Institute for Chemical and Bioengineering, ETH Zurich, Vladimir-Prelog-Weg 1-5/10, 8093, Zurich, Switzerland.

出版信息

Angew Chem Int Ed Engl. 2023 Aug 21;62(34):e202303574. doi: 10.1002/anie.202303574. Epub 2023 Jul 11.

Abstract

Cu-exchanged mordenite (MOR) is a promising material for partial CH oxidation. The structural diversity of Cu species within MOR makes it difficult to identify the active Cu sites and to determine their redox and kinetic properties. In this study, the Cu speciation in Cu-MOR materials with different Cu loadings has been determined using operando electron paramagnetic resonance (EPR) and operando ultraviolet-visible (UV/Vis) spectroscopy as well as in situ photoluminescence (PL) and Fourier-transform infrared (FTIR) spectroscopy. A novel pathway for CH oxidation involving paired [CuOH] and bare Cu species has been identified. The reduction of bare Cu ions facilitated by adjacent [CuOH] demonstrates that the frequently reported assumption of redox-inert Cu centers does not generally apply. The measured site-specific reaction kinetics show that dimeric Cu species exhibit a faster reaction rate and a higher apparent activation energy than monomeric Cu active sites highlighting their difference in the CH oxidation potential.

摘要

铜交换丝光沸石(MOR)是一种用于部分CH氧化的有前景的材料。MOR中铜物种的结构多样性使得难以识别活性铜位点并确定其氧化还原和动力学性质。在本研究中,使用原位电子顺磁共振(EPR)和原位紫外可见(UV/Vis)光谱以及原位光致发光(PL)和傅里叶变换红外(FTIR)光谱确定了不同铜负载量的Cu-MOR材料中的铜物种形态。已确定了一种涉及成对的[CuOH]和裸露铜物种的CH氧化新途径。相邻的[CuOH]促进了裸露铜离子的还原,这表明经常报道的氧化还原惰性铜中心的假设通常并不适用。所测量的位点特异性反应动力学表明,二聚体铜物种比单体铜活性位点表现出更快的反应速率和更高的表观活化能,突出了它们在CH氧化电位上的差异。

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