TY - JOUR
T1 - Engineering Dendrimer-Templated, Metal-Organic Framework-Confined Zero-Valent, Transition-Metal Catalysts
AU - Yang, Ying
AU - Noh, Hyunho
AU - Ma, Qing
AU - Wang, Rui
AU - Chen, Zhihengyu
AU - Schweitzer, Neil M.
AU - Liu, Jian
AU - Chapman, Karena W.
AU - Hupp, Joseph T.
N1 - Funding Information:
This work was supported as part of the Inorganometallic Catalyst Design Center, an EFRC funded by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences (DE-SC0012702). This work made use of EPIC and KECK II facilities of Northwestern University’s NUANCE Center, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205), the MRSEC program (NSF DMR1720139) at the Materials Research Center, the Institute for Nanotechnology (IIN), the Keck Foundation, and the State of Illinois, through the IIN. This work made use of the IMSERC facility at Northwestern University, which has received support from the NSF (CHE-1048773 and DMR-0521267), SHyNE Resource (NSF NNCI-1542205), the State of Illinois and IIN. This work made use of the Advanced Photon Source of Argonne National Lab (ANL), at DND-CAT (Sector 5), which is supported by E.I. DuPont de Nemours & Co., Northwestern University, and The Dow Chemical Co., and beamlines 17-BM and 11-ID-B. Argonne National Laboratory was supported by DOE contract no. DE-AC02-06CH11357. We thank the REACT facility at Northwestern University, which has received support from the DOE (DE-FG02-03ER15457).
Publisher Copyright:
© 2021 American Chemical Society.
PY - 2021/8/4
Y1 - 2021/8/4
N2 - We describe and experimentally illustrate a strategy for synthesizing reactant-accessible, supported arrays of well-confined, sub-nanometer to 2 nm, metal(0) clusters and particles - here, copper, palladium, and platinum. The synthesis entails (a) solution-phase binding of metal ions by a generation-2 poly(amidoamine) (PAMAM) dendrimer, (b) electrostatic uptake of metalated, solution-dissolved, and positively charged dendrimers by the negatively charged pores of a zirconium-based metal-organic framework (MOF), NU-1000, and (c) chemical reduction of the incorporated metal ions. The pH of the unbuffered solution is known to control the overall charges of both the dendrimer guests and the hierarchically porous MOF. The combined results of electron microscopy, X-ray spectroscopy, and other measurements indicate the formation and microscopically uniform spatial distributions of zero-valent, monometallic Cu, Pd, and Pt species, with sizes depending strongly on the conditions and methods used for reduction of incorporated metal ions. Access to sub-nanometer clusters is ascribed to the stabilization effects imposed by the two templates (i.e., NU-1000 and dendrimer), which significantly limit the extent to which the metal atoms aggregate; as the thermal input increases, the dendrimer template gradually decomposes, allowing a further aggregation of metal clusters inside the hexagonal mesoporous channel of the MOF template, which ultimately self-limits at 3 nm (i.e., the mesopore width of NU-1000). Using CO oxidation and n-hexene hydrogenation as model reactions in the gas and condensed phases, we show that the dual-templated metal species can act as stable, efficient heterogeneous catalysts.
AB - We describe and experimentally illustrate a strategy for synthesizing reactant-accessible, supported arrays of well-confined, sub-nanometer to 2 nm, metal(0) clusters and particles - here, copper, palladium, and platinum. The synthesis entails (a) solution-phase binding of metal ions by a generation-2 poly(amidoamine) (PAMAM) dendrimer, (b) electrostatic uptake of metalated, solution-dissolved, and positively charged dendrimers by the negatively charged pores of a zirconium-based metal-organic framework (MOF), NU-1000, and (c) chemical reduction of the incorporated metal ions. The pH of the unbuffered solution is known to control the overall charges of both the dendrimer guests and the hierarchically porous MOF. The combined results of electron microscopy, X-ray spectroscopy, and other measurements indicate the formation and microscopically uniform spatial distributions of zero-valent, monometallic Cu, Pd, and Pt species, with sizes depending strongly on the conditions and methods used for reduction of incorporated metal ions. Access to sub-nanometer clusters is ascribed to the stabilization effects imposed by the two templates (i.e., NU-1000 and dendrimer), which significantly limit the extent to which the metal atoms aggregate; as the thermal input increases, the dendrimer template gradually decomposes, allowing a further aggregation of metal clusters inside the hexagonal mesoporous channel of the MOF template, which ultimately self-limits at 3 nm (i.e., the mesopore width of NU-1000). Using CO oxidation and n-hexene hydrogenation as model reactions in the gas and condensed phases, we show that the dual-templated metal species can act as stable, efficient heterogeneous catalysts.
KW - CO oxidation
KW - PAMAM dendrimer
KW - alkene hydrogenation
KW - dual-templating
KW - metal-organic framework
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U2 - 10.1021/acsami.1c11541
DO - 10.1021/acsami.1c11541
M3 - Article
C2 - 34308623
AN - SCOPUS:85112533468
SN - 1944-8244
VL - 13
SP - 36232
EP - 36239
JO - ACS Applied Materials and Interfaces
JF - ACS Applied Materials and Interfaces
IS - 30
ER -