Issue 35, 2024

Selective conversion of methane to methanol facilitated by molecular metal–methoxy complexes via a self-correcting chemical cycle

Abstract

The controlled oxidation of methane to methanol has been an area of intense research over the past decades. Despite the efforts, the identification of an efficient catalyst with high selectivity is still elusive. Here we propose a thoroughly different strategy employing catalysts containing a metal methoxy unit. This family of catalysts has been used for the activation of C–H bonds but this is the first systematic investigation for the conversion of methane to methanol highlighting the advantages over the typically used metal oxides. Specifically, we start our investigation with an Fe(III) center coordinated by four ammonia ligands, (NH3)4FeOCH32+. Structures and energetics are reported for two mechanisms ([2+2] and proton coupled electrons transfer) and for different spin multiplicities via density functional theory, multi-reference, and coupled cluster quantum chemical calculations. The excited low-spin doublet state of this model system exhibits the best performance in terms of activation barriers and selectivity. Therefore, we then switched to the corresponding Ru(III) complex, which has a doublet ground state and manifests better performance than the doublet state of Fe(III). For both systems the activation barrier for methanol is larger than that of methane due to the interaction of the OH group of methanol with the coordinated NH3 ligands (hydrogen bonding) and/or the metal center. This observation suggests that the activation of methanol is slower, hindering its oxidation. In addition, we show that the metal–methoxy family of catalysts offers a potential mechanism that can prevent the oxidation of an activated methanol molecule (self-correcting chemical loop). This work aspires to induce experimental interest and pave the road for the development of high-performance high-selectivity methane to methanol direct conversion routes under mild conditions.

Graphical abstract: Selective conversion of methane to methanol facilitated by molecular metal–methoxy complexes via a self-correcting chemical cycle

Supplementary files

Article information

Article type
Paper
Submitted
27 5 2024
Accepted
13 8 2024
First published
14 8 2024

Phys. Chem. Chem. Phys., 2024,26, 23136-23143

Selective conversion of methane to methanol facilitated by molecular metal–methoxy complexes via a self-correcting chemical cycle

S. N. Khan, B. Quebedeaux and E. Miliordos, Phys. Chem. Chem. Phys., 2024, 26, 23136 DOI: 10.1039/D4CP02189D

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements