Oxo‐Bridged Zr Dimers as Well‐defined Models of Oxygen Vacancies on ZrO2. Issue 12 (28th February 2023)

• Record Type: Journal Article
• Authors: Wimmer, Erik J.; Klostermann, Sina V.; Ringenberg, Mark; Kästner, Johannes; Estes, Deven P.
• Is Part Of: European journal of inorganic chemistry. Volume 26:Issue 12(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-02-28
• Subjects: CO2 reduction -- hydrides -- lewis acid model -- oxygen vacancy -- zirconium; Chemistry, Inorganic -- Periodicals; Organometallic chemistry -- Periodicals; Bioinorganic chemistry -- Periodicals; Solid state chemistry -- Periodicals; 546
• DOI: 10.1002/ejic.202200709
• Languages: English
• ISSNs: 1434-1948

Abstract

Abstract: While ZrO2 is known to have a large effect on the activity and selectivity of the Cu/ZrO2 catalyst for methanol synthesis, its role in this process is poorly understood. Surface defects such as oxygen vacancies could play a role in the strong metal‐support interaction (SMSI) between Cu and ZrO2 . However, due to the complexity of the surfaces, the exact molecular nature of this interaction is not at present known. Here, we make well‐defined models of both reduced and coordinatively unsaturated surface oxygen vacancies on ZrO2 using the molecular precursor [Cp2 ZrCl]2 (μ 2 ‐O) (1 ). Complex 1 can be reduced to form a complex (2 ) containing one Zr(III) center and a bridging hydride ligand (according to EPR and IR spectroscopy) derived from C−H activation of either thf or the Cp ring. Complex 2 reacts with CO2 to largely produce CO, suggesting that surface defects with similar structures probably do not play a role in the industrial catalyst. Halide abstraction from complex 1 results in the Lewis acidic species 3, which has similar Lewis acid properties to acidic defects on the ZrO2 surface. Similarities of both of these model species to real surface oxygen vacancies and their role in the catalytic reaction are discussed. Abstract : Oxygen vacancies on ZrO2 surfaces are thought to be critical for high selectivity of MeOH over CO production during CO2 hydrogenation with Cu/ZrO2 catalysts. Here we synthesize molecular models of Zr oxygen vacancies using the precursor [Cp2 ZrCl]2 (μ 2 ‐O) (1 ) and show that reduced vacancies favor CO production.