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This content will become publicly available on January 29, 2019

Title: Extending the Compositional Range of Nanocasting in the Oxozirconium Cluster-Based Metal–Organic Framework NU-1000—A Comparative Structural Analysis

Here, the process of nanocasting in metal-organic frameworks (MOFs) is a versatile approach to modify these porous materials by introducing supporting scaffolds. The nanocast scaffolds can stabilize metal-oxo clusters in MOFs at high temperatures and modulate their chemical environments. Here we demonstrate a range of nanocasting approaches in the MOF NU-1000, which contains hexanuclear oxozirconium clusters (denoted as Zr 6 clusters) that are suitable for modification with other metals. We developed methods for introducing SiO 2, TiO 2, polymeric, and carbon scaffolds into the NU-1000 structure. The responses of NU-1000 towards different scaffold precursors were studied, including the effects on morphology, precursor distribution, and porosity after nanocasting. Upon removal of organic linkers in the MOF by calcination/pyrolysis at 500 °C or above, the Zr 6 clusters remained accessible and maintained their Lewis acidity in SiO 2 nanocast samples, whereas additional treatment was necessary for Zr 6 clusters to become accessible in carbon nanocast samples. Aggregation of Zr 6 clusters was largely prevented with SiO 2 or carbon scaffolds even after thermal treatment at 500 °C or above. In the case of titania nanocasting, NU- 1000 crystals underwent a pseudomorphic transformation, in which Zr 6 clusters reacted with titania to formmore » small oxaggregates of a Zr/Ti mixed oxide with a local structure resembling that of ZrTi 2O 6. In conclusion, the ability to maintain high densities of discrete Lewis acidic Zr 6 clusters on SiO 2 or carbon supports at high temperatures provides a starting point for designing new thermally stable catalysts.« less
Authors:
ORCiD logo [1] ;  [1] ;  [1] ; ORCiD logo [1] ; ORCiD logo [2] ;  [3] ;  [4] ; ORCiD logo [4] ; ORCiD logo [4] ; ORCiD logo [5] ; ORCiD logo [1] ; ORCiD logo [2] ;  [3] ; ORCiD logo [1]
  1. Univ. of Minnesota, Minneapolis, MN (United States)
  2. Argonne National Lab. (ANL), Argonne, IL (United States)
  3. Quantachrome Instruments, Boynton Beach, FL (United States)
  4. Northwestern Univ., Evanston, IL (United States)
  5. Northwestern Univ., Evanston, IL (United States); King Abdulaziz Univ., Jeddah (Saudi Arabia)
Publication Date:
Grant/Contract Number:
AC02-06CH11357
Type:
Accepted Manuscript
Journal Name:
Chemistry of Materials
Additional Journal Information:
Journal Volume: 30; Journal Issue: 4; Journal ID: ISSN 0897-4756
Publisher:
American Chemical Society (ACS)
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; MOFs; Metal-organic framework; NU-1000; Zr-MOFs; carbon; cluster stabilization; nanocasting; oxozirconium clusters; poly(furfuryl alcohol); silica; titania
OSTI Identifier:
1431343