Single-Atom Metal Oxide Sites as Traps for Charge Separation in the Zirconium-Based Metal-Organic Framework NDC-NU-1000

Boris V. Kramar, Brian T. Phelan, Emily A. Sprague-Klein, Benjamin T. Diroll, Sungsik Lee, Ken Ichi Otake, Rebecca Palmer, Michael W. Mara, Omar K. Farha, Joseph T. Hupp*, Lin X. Chen

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Solvothermal deposition in metal-organic frameworks (MOFs) can be used to mount single-metal-atom catalytic species at chemically reactive sites on hexa-Zr(IV)-oxy(oxo,hydroxo,aqua) nodes in nanoscale crystallites of the MOF NDC-NU-1000 in a self-limiting fashion. Upon photoexcitation of the 1,3,6,8-tetrakis(p-benzoato)pyrene chromophores of the parent framework, charge transfer may occur between the chromophores and the installed heterometal sites. Extended X-ray absorption fine structure studies revealed the single-atom nature of the installed species. A combination of steady-state and ultrafast optical spectroscopy was used to uncover evidence of a charge-separated (CS) state arising in the metalated samples. The relevant dynamics were characterized with transient photoluminescence and femtosecond transient absorption spectroscopy. We find that a titanium-oxy single-atom site gives rise to the longest lived CS species compared to cobalt and nickel in a similar arrangement. This study provides guidance in designing MOF-based catalytic systems for photocatalysis and solar fuel production.

Original languageEnglish (US)
JournalEnergy and Fuels
DOIs
StateAccepted/In press - 2021

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Fuel Technology
  • Energy Engineering and Power Technology

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