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Electrocatalytic Ammonia Oxidation with a Tailored Molecular Catalyst Heterogenized via Surface Host–Guest Complexation


Roithmeyer, Helena; Sévery, Laurent; Moehl, Thomas; Spingler, Bernhard; Blacque, Olivier; Fox, Thomas; Iannuzzi, Marcella; Tilley, S David (2024). Electrocatalytic Ammonia Oxidation with a Tailored Molecular Catalyst Heterogenized via Surface Host–Guest Complexation. Journal of the American Chemical Society, 146(1):430-436.

Abstract

Macrocyclic host mols. bound to electrode surfaces enable the complexation of catalytically active guests for mol. heterogeneous catalysis. The authors present a surface-anchored host-guest complex with the ability to electrochem. oxidize NH3 in both organic and aqueous solutions With an adamantyl motif as the binding group on the backbone of the mol. catalyst [Ru(bpy-NMe2)(tpada)(Cl)](PF6) (1) (bpy-NMe2 is 4,4′-bis(dimethylamino)-2,2′-bipyridyl, tpada is 4′-(adamantan-1-yl)-2,2′:6′,2′′-terpyridine), high binding constants with β-cyclodextrin were observed in solution (in DMSO-d6: D2O (7:3), K11 = 492 ± 21 M-1). The strong binding affinities were also transferred to a mesoporous ITO (mITO) surface functionalized with a phosphonated derivative of β-cyclodextrin. The newly designed catalyst (1) was compared to the previously reported naphthyl-substituted catalyst [Ru(bpy-NMe2)(tpnp)(Cl)](PF6) (2) (tpnp is 4′-(naphthalene-2-yl)-2,2′:6′,2′′-terpyridine) for its stability during catalysis. Despite the insulating nature of the adamantyl substituent serving as the binding group, the stronger binding of this unit to the host functionalized electrode and the resulting shorter distance between the catalytic active center and the surface led to better performance and higher stability. Both guests are able to oxidize NH3 in both organic and aqueous solutions and the host-anchored electrode can be refunctionalized multiple times (>3) following loss of the catalytic activity, without a reduction in performance. Guest 1 exhibits significantly higher stability in comparison to guest 2 toward basic conditions, which often constitutes a challenge for anchored mol. systems. NH3 oxidation in H2O led to the selective formation of NO3- with faradaic efficiencies of up to 100%.

Abstract

Macrocyclic host mols. bound to electrode surfaces enable the complexation of catalytically active guests for mol. heterogeneous catalysis. The authors present a surface-anchored host-guest complex with the ability to electrochem. oxidize NH3 in both organic and aqueous solutions With an adamantyl motif as the binding group on the backbone of the mol. catalyst [Ru(bpy-NMe2)(tpada)(Cl)](PF6) (1) (bpy-NMe2 is 4,4′-bis(dimethylamino)-2,2′-bipyridyl, tpada is 4′-(adamantan-1-yl)-2,2′:6′,2′′-terpyridine), high binding constants with β-cyclodextrin were observed in solution (in DMSO-d6: D2O (7:3), K11 = 492 ± 21 M-1). The strong binding affinities were also transferred to a mesoporous ITO (mITO) surface functionalized with a phosphonated derivative of β-cyclodextrin. The newly designed catalyst (1) was compared to the previously reported naphthyl-substituted catalyst [Ru(bpy-NMe2)(tpnp)(Cl)](PF6) (2) (tpnp is 4′-(naphthalene-2-yl)-2,2′:6′,2′′-terpyridine) for its stability during catalysis. Despite the insulating nature of the adamantyl substituent serving as the binding group, the stronger binding of this unit to the host functionalized electrode and the resulting shorter distance between the catalytic active center and the surface led to better performance and higher stability. Both guests are able to oxidize NH3 in both organic and aqueous solutions and the host-anchored electrode can be refunctionalized multiple times (>3) following loss of the catalytic activity, without a reduction in performance. Guest 1 exhibits significantly higher stability in comparison to guest 2 toward basic conditions, which often constitutes a challenge for anchored mol. systems. NH3 oxidation in H2O led to the selective formation of NO3- with faradaic efficiencies of up to 100%.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Scopus Subject Areas:Physical Sciences > Catalysis
Physical Sciences > General Chemistry
Life Sciences > Biochemistry
Physical Sciences > Colloid and Surface Chemistry
Uncontrolled Keywords:Colloid and Surface Chemistry, Biochemistry, General Chemistry, Catalysis
Language:English
Date:10 January 2024
Deposited On:20 Jan 2024 14:35
Last Modified:31 Mar 2024 01:38
Publisher:American Chemical Society (ACS)
ISSN:0002-7863
Additional Information:This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of the American Chemical Society copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://pubs.acs.org/doi/10.1021/jacs.3c09725
OA Status:Closed
Publisher DOI:https://doi.org/10.1021/jacs.3c09725
PubMed ID:38134360
Project Information:
  • : FunderDr. Helmut Legerlotz-Stiftung
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  • : Project Title
  • : FunderUniversit?t Z?rich
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