Metal–Organic Frameworks (MOFs) are nanostructured porous materials made up by metal cations and organic linkers forming three-dimensional structures. Since their discovery, the local properties of metal centers in MOFs have often been studied with hard X-ray absorption spectroscopy that is not a surface sensitive technique. Here, we employ the ambient-pressure soft X-ray absorption spectroscopy, using a newly developed experimental setup, to unveil the formation mechanism of surface defective sites in the prototypical Cu(II)-based MOF HKUST-1, as well as the reactivity and selectivity of these sites towards CO2 from the analysis of the Cu L3 -edge near edge X-ray absorption spectroscopy (NEXAFS) data. We observe that, upon thermal heating, Cu(I) defects are formed more abundantly on the surface of the material as compared to the bulk, a process that is almost fully reversed when the MOF is exposed to CO2 , even when mixed with H2. Additionally, we propose a structure and a formation mechanism for such defective sites, supported by theoretical DFT-based calculations.

Insights into structure and reactivity of MOFs by ambient pressure soft X-ray absorption spectroscopy / Tofoni, Alessandro; Tavani, Francesco; Braglia, Luca; Colombo, Valentina; Torelli, Piero; D’Angelo, Paola. - In: RADIATION PHYSICS AND CHEMISTRY. - ISSN 0969-806X. - 213:(2023), pp. 1-6. [10.1016/j.radphyschem.2023.111243]

Insights into structure and reactivity of MOFs by ambient pressure soft X-ray absorption spectroscopy

Alessandro Tofoni;Francesco Tavani;Piero Torelli;Paola D’Angelo
2023

Abstract

Metal–Organic Frameworks (MOFs) are nanostructured porous materials made up by metal cations and organic linkers forming three-dimensional structures. Since their discovery, the local properties of metal centers in MOFs have often been studied with hard X-ray absorption spectroscopy that is not a surface sensitive technique. Here, we employ the ambient-pressure soft X-ray absorption spectroscopy, using a newly developed experimental setup, to unveil the formation mechanism of surface defective sites in the prototypical Cu(II)-based MOF HKUST-1, as well as the reactivity and selectivity of these sites towards CO2 from the analysis of the Cu L3 -edge near edge X-ray absorption spectroscopy (NEXAFS) data. We observe that, upon thermal heating, Cu(I) defects are formed more abundantly on the surface of the material as compared to the bulk, a process that is almost fully reversed when the MOF is exposed to CO2 , even when mixed with H2. Additionally, we propose a structure and a formation mechanism for such defective sites, supported by theoretical DFT-based calculations.
2023
MOF; AP-NEXAFS; Operando; materials; gas absorption; carbon dioxide
01 Pubblicazione su rivista::01a Articolo in rivista
Insights into structure and reactivity of MOFs by ambient pressure soft X-ray absorption spectroscopy / Tofoni, Alessandro; Tavani, Francesco; Braglia, Luca; Colombo, Valentina; Torelli, Piero; D’Angelo, Paola. - In: RADIATION PHYSICS AND CHEMISTRY. - ISSN 0969-806X. - 213:(2023), pp. 1-6. [10.1016/j.radphyschem.2023.111243]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/1691320
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