Synthesis and Structure-Activity Characterization of a Single-Site MoO2Catalytic Center Anchored on Reduced Graphene Oxide

Yiqi Liu, Jiaqi Li, Anusheela Das, Hacksung Kim, Leighton O. Jones, Qing Ma, Michael J. Bedzyk, George C. Schatz*, Yosi Kratish, Tobin J. Marks

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

22 Scopus citations

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 languageEnglish (US)
Pages (from-to)21532-21540
Number of pages9
JournalJournal of the American Chemical Society
Volume143
Issue number51
DOIs
StatePublished - Dec 29 2021

Funding

Financial support was provided by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Award DOE DE-FG02-03ER15457 to the Institute for Catalysis in Energy Processes (ICEP) at Northwestern University (NU). This work made use of IMSERC facilities at NU, which have received support from Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-2025633), Int. Institute of Nanotechnology (IIN), and NU. This work made use of the NU QBIC supported by NASA Ames Research Center Grant NNA04CC36G. This work made use of the Keck-II and XRD facilities at NU supported by SHyNE, NSF-MRSEC program (DMR-1720139), and IIN. This work made use of the REACT Facility of NU’s Center for Catalysis and Surface Science supported by a grant from the DOE (DE-SC0001329). This work used the DuPont–Northwestern–Dow Collaborative Access Team (DND-CAT) 5BM-D beamline at the Advanced Photon Source (APS). DND-CAT is supported by NU, E. I. DuPont de Nemours & Co., and The Dow Chemical Company. The APS is supported by DOE at Argonne National Laboratory under Contract DE-AC02-06CH11357. This research was supported in part by the computational resources and staff contributions provided by the Quest High Performance Computing Facility at NU, which is jointly supported by the Office of the Provost, the Office for Research, and NU Information Technology. We thank C. L. Stern of IMSERC, S. Alayoglu and N. M. Schweitzer of REACT, A. M. Arinaga and Dr. Y. Gao of NU, and Dr. Alexander Kaushansky of the Technion Israel Institute of Technology for helpful insights and discussions.

ASJC Scopus subject areas

  • Catalysis
  • General Chemistry
  • Biochemistry
  • Colloid and Surface Chemistry

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