X-RAY SPECTROSCOPY STUDIES OF Ti-BASED METAL ORGANIC FRAMEWORKS

Long, Conor L

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https://hdl.handle.net/2142/122698 Copy

Description

Title

X-RAY SPECTROSCOPY STUDIES OF Ti-BASED METAL ORGANIC FRAMEWORKS

Author(s)

Long, Conor L

Contributor(s)

Lockard, Jenny V.

Issue Date

2023-06-20

Keyword(s)

Mini-symposium: Spectroscopy at Large-scale Facilities

Abstract

Some Ti-based metal organic frameworks (MOFs) have demonstrated photocatalytic properties. MIL125-NH₂ is a well-studied Ti-based MOF consisting of titanium-oxo clusters connected via amino terephthalic acid linkers. This structure possesses a stable, long-lived charge separated excited state in which, upon photoexcitation, an electron migrates from a linker to the metal cluster. The band structure of this framework can be modified through the replacement of Ti metal sites with d block transition metals via a direct synthesis pathway. However, further research is required on the underlying electronic structure and excited state behavior of the modified framework. Fundamental steady state and time resolved X-ray spectroscopy experiments have been carried out in order to determine the effects of heterometal doping concentration on the charge separation lifetime and the electronic environment of MIL125-NH₂. Fe K-edge X-ray transient absorption (XTA) measurements have been conducted, which show that doped MIL125-NH₂ has a long-lived excited state lifetime component of over 20 microseconds, due to iron trap sites on the metal ring. The long-lived charge separation excited state is seen even in higher doping levels, as the framework inhibits charge recombination. Ti K-β resonant x-ray emission spectroscopy (RXES) measurements show a shift in pre-edge resonant features towards lower emission energy, with the inclusion of iron heterometals. Localized d transitions on the Ti seem to be less intense with the addition of Fe into the MOF structure.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

Text

Language

eng

Handle URL

https://hdl.handle.net/2142/122698

DOI

https://doi.org/10.15278/isms.2023.7251

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