Issue 21, 2020

Enhancing catalytic alkane hydroxylation by tuning the outer coordination sphere in a heme-containing metal–organic framework

Abstract

Catalytic heme active sites of enzymes are sequestered by the protein superstructure and are regulated by precisely defined outer coordination spheres. Here, we emulate these protective functions in the porphyrinic metal–organic framework PCN-224 by post-synthetic acetylation and subsequent hydroxylation of the Zr6 nodes. A suite of physical methods demonstrates that both transformations preserve framework structure, crystallinity, and porosity without modifying the inner coordination spheres of the iron sites. Single-crystal X-ray analyses establish that acetylation replaces the mixture of formate, benzoate, aqua, and terminal hydroxo ligands at the Zr6 nodes with acetate ligands, and hydroxylation affords nodes with seven-coordinate, hydroxo-terminated Zr4+ ions. The chemical influence of these reactions is probed with heme-catalyzed cyclohexane hydroxylation as a model reaction. By virtue of passivated reactive sites at the Zr6 nodes, the acetylated framework oxidizes cyclohexane with a yield of 68(8)%, 2.6-fold higher than in the hydroxylated framework, and an alcohol/ketone ratio of 5.6(3).

Graphical abstract: Enhancing catalytic alkane hydroxylation by tuning the outer coordination sphere in a heme-containing metal–organic framework

Supplementary files

Article information

Article type
Edge Article
Submitted
28 Mar 2020
Accepted
07 May 2020
First published
07 May 2020
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2020,11, 5447-5452

Enhancing catalytic alkane hydroxylation by tuning the outer coordination sphere in a heme-containing metal–organic framework

D. Z. Zee and T. D. Harris, Chem. Sci., 2020, 11, 5447 DOI: 10.1039/D0SC01796E

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