X-ray Characterization of a Metal-organic Framework During Dehydration and CO2 Adsorption

Published

June 1, 2023

Author(s)

Evan Jahrman, Huong Giang Nguyen, Berc Kalanyan

Abstract

X-ray absorption spectroscopies are well-established for the purpose of interrogating the structure about metal sites. Often, these methods also exhibit favorable properties for studying chemical systems under their functioning conditions. This is particularly attractive for adsorbent materials, where descriptions of adsorbate-adsorbent interactions and tools to monitor the structural evolution of each are needed to inform material designs in critical applications. Here, we examine one system, Cu-BTC, a well-studied metal-organic framework (MOF) capable of adsorbing a litany of gases, including CO2. This article reports Cu K-edge X-ray absorption fine structure (XAFS) measurements performed throughout the material's activation process, which dehydrated the material at elevated temperatures, and adsorption of CO2 at a variety of partial pressures. Moreover, the design of a cell capable of heating and flowing gas over an adsorbent material is detailed. Analyzing the extended X-ray absorption fine structure (EXAFS) results quantified the bond distances and coordination numbers describing the immediate chemical environment of the system's Cu atoms under each set of environmental conditions. Here, the technique revealed little sensitivity to changes in the local atomic structure arising from the adsorbed molecules. These findings are explained in the context of the scattering amplitudes of the relevant paths. In contrast, significant spectral changes were observed in the X-ray absorption near edge structure (XANES) results, suggesting the adsorbent-adsorbate interactions influence the underlying material's electronic structure.

Proceedings Title

Advances in X-ray Analysis

Volume

66

Conference Dates

August 1-5, 2022

Conference Location

Rockville, MD, US

Conference Title

Denver X-ray Conference

Pub Type

Conferences

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Keywords

XANES, XAFS, MOF, Adsorption, CO2

Citation

Jahrman, E. , Nguyen, H. and Kalanyan, B. (2023), X-ray Characterization of a Metal-organic Framework During Dehydration and CO2 Adsorption, Advances in X-ray Analysis, Rockville, MD, US, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=935409 (Accessed April 29, 2024)