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Title: Chemoselective single-site Earth-abundant metal catalysts at metal–organic framework nodes

Abstract

Earth-abundant metal catalysts are critically needed for sustainable chemical synthesis. Here we report a simple, cheap and effective strategy of producing novel earth-abundant metal catalysts at metal–organic framework (MOF) nodes for broad-scope organic transformations. The straightforward metalation of MOF secondary building units (SBUs) with cobalt and iron salts affords highly active and reusable single-site solid catalysts for a range of organic reactions, including chemoselective borylation, silylation and amination of benzylic C–H bonds, as well as hydrogenation and hydroboration of alkenes and ketones. Our structural, spectroscopic and kinetic studies suggest that chemoselective organic transformations occur on site-isolated, electron-deficient and coordinatively unsaturated metal centres at the SBUs via σ-bond metathesis pathways and as a result of the steric environment around the catalytic site. MOFs thus provide a novel platform for the development of highly active and affordable base metal catalysts for the sustainable synthesis of fine chemicals.

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
USDOE; National Science Foundation (NSF)
OSTI Identifier:
1330241
Resource Type:
Journal Article
Resource Relation:
Journal Name: Nature Communications; Journal Volume: 7; Journal Issue: 2016
Country of Publication:
United States
Language:
ENGLISH
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 36 MATERIALS SCIENCE

Citation Formats

Manna, Kuntal, Ji, Pengfei, Lin, Zekai, Greene, Francis X., Urban, Ania, Thacker, Nathan C., and Lin, Wenbin. Chemoselective single-site Earth-abundant metal catalysts at metal–organic framework nodes. United States: N. p., 2016. Web. doi:10.1038/ncomms12610.
Manna, Kuntal, Ji, Pengfei, Lin, Zekai, Greene, Francis X., Urban, Ania, Thacker, Nathan C., & Lin, Wenbin. Chemoselective single-site Earth-abundant metal catalysts at metal–organic framework nodes. United States. doi:10.1038/ncomms12610.
Manna, Kuntal, Ji, Pengfei, Lin, Zekai, Greene, Francis X., Urban, Ania, Thacker, Nathan C., and Lin, Wenbin. 2016. "Chemoselective single-site Earth-abundant metal catalysts at metal–organic framework nodes". United States. doi:10.1038/ncomms12610.
@article{osti_1330241,
title = {Chemoselective single-site Earth-abundant metal catalysts at metal–organic framework nodes},
author = {Manna, Kuntal and Ji, Pengfei and Lin, Zekai and Greene, Francis X. and Urban, Ania and Thacker, Nathan C. and Lin, Wenbin},
abstractNote = {Earth-abundant metal catalysts are critically needed for sustainable chemical synthesis. Here we report a simple, cheap and effective strategy of producing novel earth-abundant metal catalysts at metal–organic framework (MOF) nodes for broad-scope organic transformations. The straightforward metalation of MOF secondary building units (SBUs) with cobalt and iron salts affords highly active and reusable single-site solid catalysts for a range of organic reactions, including chemoselective borylation, silylation and amination of benzylic C–H bonds, as well as hydrogenation and hydroboration of alkenes and ketones. Our structural, spectroscopic and kinetic studies suggest that chemoselective organic transformations occur on site-isolated, electron-deficient and coordinatively unsaturated metal centres at the SBUs via σ-bond metathesis pathways and as a result of the steric environment around the catalytic site. MOFs thus provide a novel platform for the development of highly active and affordable base metal catalysts for the sustainable synthesis of fine chemicals.},
doi = {10.1038/ncomms12610},
journal = {Nature Communications},
number = 2016,
volume = 7,
place = {United States},
year = 2016,
month = 8
}
  • We report here the synthesis of robust and porous metal–organic frameworks (MOFs), M-MTBC (M = Zr or Hf), constructed from the tetrahedral linker methane-tetrakis(p-biphenylcarboxylate) (MTBC) and two types of secondary building units (SBUs): cubic M 82-O) 82-OH) 4 and octahedral M6(μ 3-O) 43-OH) 4. While the M 6-SBU is isostructural with the 12-connected octahedral SBUs of UiO-type MOFs, the M 8-SBU is composed of eight MIV ions in a cubic fashion linked by eight μ 2-oxo and four μ 2-OH groups. The metalation of Zr-MTBC SBUs with CoCl 2, followed by treatment with NaBEt 3H, afforded highlymore » active and reusable solid Zr-MTBC-CoH catalysts for the hydrogenation of alkenes, imines, carbonyls, and heterocycles. Zr-MTBC-CoH was impressively tolerant of a range of functional groups and displayed high activity in the hydrogenation of tri- and tetra-substituted alkenes with TON > 8000 for the hydrogenation of 2,3-dimethyl-2-butene. Our structural and spectroscopic studies show that site isolation of and open environments around the cobalt-hydride catalytic species at Zr 8-SBUs are responsible for high catalytic activity in the hydrogenation of a wide range of challenging substrates. MOFs thus provide a novel platform for discovering and studying new single-site base-metal solid catalysts with enormous potential for sustainable chemical synthesis.« less
  • We present the first example of a single-site main group catalyst stabilized by a metal$-$ organic framework (MOF) for organic transformations.
  • The metal–organic framework NU-1000, with Zr 6-oxo, hydroxo, and aqua nodes, was modified by incorporation of hydroxylated Al(iii) ions by ALD-like chemistry with [Al(CH 3) 2(iso-propoxide)] 2followed by steam (ALD = atomic layer deposition). Al ions were installed to the extent of approximately 7 per node. Single-site iridium diethylene complexes were anchored to the nodes of the modified and unmodified MOFs by reaction with Ir(C 2H 4) 2(acac) (acac = acetylacetonate) and converted to Ir(CO) 2complexes by treatment with CO. Infrared spectra of these supported complexes show that incorporation of Al weakened the electron donor tendency of the MOF. Correspondingly,more » the catalytic activity of the initial supported iridium complexes for ethylene hydrogenation increased, as did the selectivity for ethylene dimerization. The results of density functional theory calculations with a simplified model of the nodes incorporating Al(iii) ions are in qualitative agreement with some catalyst performance data.« less
  • The Zr 6 nodes of the metal–organic frameworks (MOFs) UiO-66 and UiO-67 are metal oxide clusters of atomic precision and can be used as catalyst supports. The bonding sites on these nodes—that is, hydrogen-bonded H 2O/OH groups on UiO-67 and non-hydrogen-bonded terminal OH groups on UiO-66—were regulated by modulation of the MOF syntheses. Ir(C 2H 4) 2(C 5H 7O 2) complexes reacted with these sites to give site-isolated Ir(C 2H 4) 2 complexes, each anchored to the node by two Ir–Onode bonds. The supported iridium complexes on these sites have been characterized by infrared (IR) and extended X-ray absorption finemore » structure (EXAFS) spectroscopies and density functional theory calculations. The ethylene ligands on iridium are readily replaced by CO, and the ν CO frequencies of the resultant complexes and those of comparable complexes reported elsewhere show that the support electron-donor tendencies increase in the order HY zeolite << UiO-66 < UiO-67 (= NU-1000) < ZrO 2 < MgO. The sharpness of the IR ν CO bands shows that the degree of uniformity of the support bonding sites decreases in the order ZrO 2 ≈ UiO-67 ≈ NU-1000 < MgO < UiO-66 << HY zeolite. The reactivity of supported Ir(CO) 2 complexes with C2H4 to form Ir(C 2H 4)(CO) and Ir(C 2H 4) 2(CO) is influenced by the support electron-donor properties, with the reactivity increasing in the order MgO = ZrO 2 = NU-1000 (not reactive) < UiO-66 < UiO-67 << HY zeolite. Density functional theory calculations characterizing the complexes supported on NU-1000, UiO-66/67, and HY zeolite concur with the use of the calculated ν CO bands as indicators of electron-donor properties of the supported metal catalysts. Our calculations also show that the reactivity of the supported Ir(CO) 2 complexes with C 2H 4 is correlated with the electron-donor properties of the iridium center. Lastly, the supported Ir(C 2H 4) 2 samples are precatalysts for ethylene hydrogenation and ethylene dimerization, with the activity for each reaction increasing with increasing electron-withdrawing strength of the support.« less