Abstract
Molecularly derived single-site heterogeneous catalysts can bridge the understanding and performance gaps between conventional homogeneous and heterogeneous catalysis, guiding the rational design of next-generation catalysts. While impressive advances have been made with well-defined oxide supports, the structural complexity of other supports and the nature of the grafted surface species present an intriguing challenge. In this study, single-site Mo(-O)2 species grafted onto reduced graphene oxide (rGO/MoO2) are characterized by XPS, DRIFTS, powder XRD, N2 physisorption, NH3-TPD, aqueous contact angle, active site poisoning assay, Mo EXAFS, model compound single-crystal XRD, DFT, and catalytic performance. NH3-TPD reveals that the anchored MoO2 moiety is not strongly acidic, while Mo 3d5/2 XPS assigns the oxidation state as Mo(VI), and XRD shows little rGO periodicity change on MoO2 grafting. Contact angle analysis shows that MoO2 grafting consumes rGO surface polar groups, yielding a more hydrophobic surface. The rGO/MoO2 DRIFTS assigns features at 959 and 927 cm-1 to the symmetric and antisymmetric Mo-O stretching modes, respectively, of an isolated cis-(O-Mo-O) moiety, in agreement with DFT computation. Moreover, the Mo EXAFS rGO/MoO2 structural data are consistent with isolated (C-O)2-Mo(-O)2 species having two Mo-O bonds and two Mo-O bonds at distances of 1.69(3) and 1.90(3) Å, respectively. rGO/MoO2 is also more active than the previously reported AC/MoO2 catalyst, with reductive carbonyl coupling TOFs approaching 1.81 × 103 h-1. rGO/MoO2 is environmentally robust and multiply recyclable with 69 ± 2% of the Mo sites catalytically significant. Overall, rGO/MoO2 is a structurally well-defined and versatile single-site Mo(VI) dioxo heterogeneous catalytic system.
Original language | English (US) |
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Pages (from-to) | 21532-21540 |
Number of pages | 9 |
Journal | Journal of the American Chemical Society |
Volume | 143 |
Issue number | 51 |
DOIs | |
State | Published - Dec 29 2021 |
ASJC Scopus subject areas
- Catalysis
- Chemistry(all)
- Biochemistry
- Colloid and Surface Chemistry
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CCDC 2077947: Experimental Crystal Structure Determination
Liu, Y. (Contributor), Li, J. (Contributor), Das, A. (Contributor), Kim, H. (Contributor), Jones, L. O. (Contributor), Ma, Q. (Contributor), Bedzyk, M. J. (Contributor), Schatz, G. C. (Contributor), Kratish, Y. (Contributor) & Marks, T. J. (Contributor), Cambridge Crystallographic Data Centre, 2021
DOI: 10.5517/ccdc.csd.cc27r8kv, http://www.ccdc.cam.ac.uk/services/structure_request?id=doi:10.5517/ccdc.csd.cc27r8kv&sid=DataCite
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CCDC 2077942: Experimental Crystal Structure Determination
Liu, Y. (Contributor), Li, J. (Contributor), Das, A. (Contributor), Kim, H. (Contributor), Jones, L. O. (Contributor), Ma, Q. (Contributor), Bedzyk, M. J. (Contributor), Schatz, G. C. (Contributor), Kratish, Y. (Contributor) & Marks, T. J. (Contributor), Cambridge Crystallographic Data Centre, 2021
DOI: 10.5517/ccdc.csd.cc27r8dp, http://www.ccdc.cam.ac.uk/services/structure_request?id=doi:10.5517/ccdc.csd.cc27r8dp&sid=DataCite
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