Elucidating the Nanoparticle-Metal Organic Framework Interface of Pt@ZIF-8 Catalysts

Cassandra L. Whitford, Casey J. Stephenson, Diego A. Gómez-Gualdrón, Joseph T Hupp, Omar K. Farha, Randall Q. Snurr, Peter C Stair

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

Composites of metal nanoparticles encapsulated in metal-organic frameworks (NP@MOFs) have emerged as heterogeneous catalysts for regioselective reactions. While numerous NP@MOF composite combinations have been synthesized, characterization of the nanoparticle-MOF interface and the encapsulated nanoparticle surface have yet to be determined. In this work, Pt@ZIF-8 synthesized by the controlled encapsulation method was chosen as a representative NP@MOF, and in situ characterization methods coupled with density functional theory (DFT) calculations were used to probe the nanoparticle surface. CO adsorption diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) revealed that Pt@ZIF-8 exhibits red-shifted linear- and bridge-bound CO peaks and a linear peak associated with cationic Pt. DFT calculations and 1H NMR suggest that these sites arise from the binding and electronic donation of the MOF linker, 2-methylimidazole, to the Pt surface. DRIFTS under argon reveals that linker fragments may be present on the Pt nanoparticle surface, suggesting a reaction between the nanoparticle and the MOF linker during controlled encapsulation synthesis. Finally, CO oxidation reveals via DRIFTS that the red-shifted linear CO and bridging CO sites are active sites, while the cationic Pt is not. Overall, these results show that Pt@ZIF-8 contains unique Pt surface sites and indicate that the nanoparticle-MOF interface contains a heterogeneous mixture of framework 2-methylimidazole, free-standing 2-methylimidazole, and linker fragments. These findings expose the complex nature of the nanoparticle surface in NP@MOF composites and demonstrate the importance of characterizing their surface to understand their catalytic behavior.

Original languageEnglish
Pages (from-to)25079-25091
Number of pages13
JournalJournal of Physical Chemistry C
Volume121
Issue number45
DOIs
Publication statusPublished - Nov 16 2017

Fingerprint

Metal nanoparticles
Nanoparticles
catalysts
nanoparticles
Catalysts
Carbon Monoxide
metals
Metals
Fourier transform infrared spectroscopy
Encapsulation
reflectance
Density functional theory
Composite materials
composite materials
fragments
spectroscopy
density functional theory
Argon
Binding Sites
Nuclear magnetic resonance

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

Cite this

Elucidating the Nanoparticle-Metal Organic Framework Interface of Pt@ZIF-8 Catalysts. / Whitford, Cassandra L.; Stephenson, Casey J.; Gómez-Gualdrón, Diego A.; Hupp, Joseph T; Farha, Omar K.; Snurr, Randall Q.; Stair, Peter C.

In: Journal of Physical Chemistry C, Vol. 121, No. 45, 16.11.2017, p. 25079-25091.

Research output: Contribution to journalArticle

Whitford, CL, Stephenson, CJ, Gómez-Gualdrón, DA, Hupp, JT, Farha, OK, Snurr, RQ & Stair, PC 2017, 'Elucidating the Nanoparticle-Metal Organic Framework Interface of Pt@ZIF-8 Catalysts', Journal of Physical Chemistry C, vol. 121, no. 45, pp. 25079-25091. https://doi.org/10.1021/acs.jpcc.7b06773
Whitford CL, Stephenson CJ, Gómez-Gualdrón DA, Hupp JT, Farha OK, Snurr RQ et al. Elucidating the Nanoparticle-Metal Organic Framework Interface of Pt@ZIF-8 Catalysts. Journal of Physical Chemistry C. 2017 Nov 16;121(45):25079-25091. https://doi.org/10.1021/acs.jpcc.7b06773
Whitford, Cassandra L. ; Stephenson, Casey J. ; Gómez-Gualdrón, Diego A. ; Hupp, Joseph T ; Farha, Omar K. ; Snurr, Randall Q. ; Stair, Peter C. / Elucidating the Nanoparticle-Metal Organic Framework Interface of Pt@ZIF-8 Catalysts. In: Journal of Physical Chemistry C. 2017 ; Vol. 121, No. 45. pp. 25079-25091.
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