Systematic Engineering of Single Substitution in Zirconium Metal-Organic Frameworks toward High-Performance Catalysis

J Am Chem Soc. 2017 Dec 27;139(51):18590-18597. doi: 10.1021/jacs.7b09553. Epub 2017 Dec 8.

Abstract

Zirconium-based metal-organic frameworks (Zr-MOFs) exhibit great structural tunability and outstanding chemical stability, rendering them promising candidates for a wide range of practical applications. In this work, we synthesized a series of isostructural PCN-224 analogues functionalized by ethyl, bromo, chloro, and fluoro groups on the porphyrin unit, which allowed us to explicitly study the effects of electron-donating and electron-withdrawing substituents on catalytic performance in MOFs. Owing to the different electronic properties of ethyl, bromo, chloro, and fluoro substitutes, the molecular-level control over the chemical environment surrounding a catalytic center could be readily achieved in our MOFs. To investigate the effects of these substitutes on catalytic activity and selectivity, the oxidation of 3-methylpentane to corresponding alcohols and ketones was utilized as a model reaction. Within these five analogues of PCN-224, an extremely high turnover number of 7680 and turnover frequency of 10 240 h-1 was achieved by simply altering the substitutes on porphyrin rings. Moreover, a remarkable 99% selectivity of the tertiary alcohol over the five other possible by-products are realized. We demonstrate that this strategy can be used to efficiently screen a suitable peripheral environment around catalytic cores in MOFs for catalysis.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Alcohols / chemistry
  • Catalysis
  • Electrons
  • Ketones / chemistry
  • Metal-Organic Frameworks / chemical synthesis*
  • Metal-Organic Frameworks / chemistry*
  • Oxidation-Reduction
  • Pentanes / chemistry
  • Porphyrins / chemistry
  • Zirconium / chemistry*

Substances

  • Alcohols
  • Ketones
  • Metal-Organic Frameworks
  • Pentanes
  • Porphyrins
  • Zirconium
  • 3-methylpentane