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Nanocasting provides thermally-stable scaffold for MOF catalytic metal sites

Recent research from the research group of Professor

Metal organic frameworks (MOFs) are porous materials that provide a good platform for heterogeneous catalysis involving single metal sites. Most MOFs, however, are not stable above 350 ˚C and therefore cannot be used to catalyze reactions that occur only at high temperatures.  A collaborative team among the University of Minnesota, Northwestern University, and Argonne National Laboratory now present an approach called nanocasting to provide a more thermally stable scaffold for MOF-based catalytic metal sites, making them suitable for high temperature catalysis.

The study was spearheaded by Camille Malonzo in the group of Professor Andreas Stein at the University Minnesota, who developed the nanocasting method for MOFs. The MOF studied in this work is NU-1000, made by the groups of Omar Farha and Joseph Hupp at Northwestern University. Collaborators from UMN include R. Lee Penn, Connie Lu, Jason Myers, Michael Tsapatsis and Laura Gagliardi, who aided in the characterization, testing and theoretical studies of the materials. Valuable structural information was also provided by Karena Chapman of the synchroton X-ray facility at Argonne National Laboratory. 

The work has been highlighted by C&EN (Chemical and Engineering News, Volume 94, Issue 7, p. 23). Full details of the study are available at Malonzo, et al. “Thermal Stabilization of Metal–Organic Framework-Derived Single-Site Catalytic Clusters through Nanocasting,” Journal of the American Chemical Society (2016). DOI: 10.1021/jacs.5b12688

This project was supported in part by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences under award DE-SC0012702 (Inorganometallic Catalyst Design Center).

Nanocasting is the nanoscale counterpart of the industrial casting process in which a fluid is poured into a mold and allowed to solidify, taking the shape of the mold. For the case of the MOF NU-1000, condensing tetramethylorthosilicate in its pores resulted in the formation of a silica layer that lined the pore walls of the MOF. The silica layer then served as a secondary scaffold for the MOF metal sites, keeping them catalytically active even after the organic linkers in the MOF were lost at high temperatures.