Pore-Templated Growth of Catalytically Active Gold Nanoparticles

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Pore-templated Growth of Catalytically-Active Gold Nanoparticles within a Metal–Organic Framework Subhadip Goswami, Hyunho Noh, Louis R. Redfern, Ken-ichi Otake, ChungWei Kung, Yuexing Cui, Karena W Chapman, Omar K. Farha, and Joseph T. Hupp Chem. Mater., Just Accepted Manuscript • DOI: 10.1021/acs.chemmater.8b04983 • Publication Date (Web): 25 Feb 2019 Downloaded from http://pubs.acs.org on February 28, 2019

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Chemistry of Materials

Pore-templated Growth of Catalytically-Active Gold Nanoparticles within a Metal–Organic Framework Subhadip Goswami,a Hyunho Noh,a Louis R. Redfern,a,b Ken-ichi Otake,a,† Chung-Wei Kung,a,‡ Yuexing Cui,a Karena W. Chapman,b,c Omar K. Farha ,a,* Joseph T. Hupp a,* aDepartment bX-ray

of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA.

Science Division, Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Ave, Lemont, IL, 60439,

USA. cDepartment

of Chemistry, Stony Brook University, Stony Brook, NY 11764-3400, USA.

ABSTRACT:

Obtaining persistently well-dispersed gold nanoparticles (AuNPs) on solid support with optimum particle size for heterogeneous catalysis can be challenging. Here, we report on the channel-templated growth of AuNPs within a stable zirconiumbased metal−organic framework, NU-1000, via channel-anchored monometallic precursors. Pair distribution function analysis of total X-ray scattering by the incorporated face-centered-cubic nanoparticles reveals a bimodal size distribution, with ca. 98% of the enshrouded nanoparticles having a diameter that closely reflects the ~10 Å width of triangular pores and with ca. 2% closely reflecting the ~31 Å width of hexagonal pores of NU-1000. The resulting material is catalytically active (and recyclable) for condensed-phase hydrogenation of 4-nitrophenol to 4aminophenol.

The chemistry of gold nanoparticles (AuNP) is an intriguing field of study owing, in part, to the particles’: a) unusual visibleregion optical properties (plasmonic properties),1-6 b) potential utility in chemical sensing, including DNA sensing,7, 8 c) potential usefulness for biomedical diagnostics or therapeutics,9 and d) catalytic properties where Au atoms on the exterior of suitably sized particles are effective for chemical,10 electrochemical,11 and/or photochemical catalysis.12-14 For many of these applications, including catalysis, the particles’ size,15,16,17 morphology, extent of isolation vs. aggregation, and/or the presence or absence of organic capping groups, are crucial variables. For heterogeneous catalysis of gas phase reactions, the nature and extent of AuNP/support interactions are also crucial variables. Standard supports include moderately high area TiO2,18 CeO2,19 or SiO2.20 While these supports can be effective for isolating AuNPs from each other, they are typically indiscriminate with regard to the size of particles supported. In turn, this may limit attempts to achieve NP size uniformity. For certain catalytic applications, isolated AuNPs having diameters ca. 1 to 2 nm appear to be uniquely effective, and therefore, desirable.21, 22 Here we report the use of a porous (~2,200 m2/g) and chemically robust metal–organic framework (MOF) material, NU-1000,23, 24 as both a particle-size-defining template and as a particle-isolating catalyst support. Notably, the hierarchical porosity of the selected MOF ensures that candidate molecular reactants can readily permeate the MOF and reach catalytic AuNP sites. We note that NP isolation within porous MOFs is not without precedent. The two most common approaches are: 1) physisorption or ion-exchange of

suitable molecular or atomic precursors within the MOF, followed by reduction of metals to oxidation-state zero and spontaneous agglomeration to form particles,25-33 and 2) growth of MOF crystallites around pre-synthesized NPs in solution.31, 34, 35 The former approach is often complicated by growth of particles beyond the bounds of individual MOF pores29, 30 (with some notable exceptions27, 31-33, 36, 37) – a not altogether surprising finding given that metallic bonding is typically stronger than metal-ligand (e.g., node-linker) bonding. The latter approach is, to a large extent, materials-general – working equally well for nanoparticulate metals, semiconductors, or insulators.35 In our hands, however, the method has proven difficult to implement with particles of less than a few nm. In contradistinction to the above-cited studies, here we have obtained AuNPs by first installing, as nonstructural ligands, species capable of organometallic bond formation with Au(I),38 but not with neutral Au(0) atoms. Specifically, we used solvent-assisted ligand installation (SALI) to attach 4-carboxy-phenylacetylene (PA) units to the eight-connected hexa-zirconium(IV)aqua,hydroxo,oxo nodes of NU-1000 (Scheme 1). We then replaced the acetylene proton on each grafted ligand with a monometallic Au(I)PEt3+ ion (PEt3 = triethylphosphine). Finally, we chemically reduced the Au(I) sites to Au(0). Reduction is accompanied by release of gold atoms from grafted phenylacetylides, diffusion of the atoms through the framework, and (as detailed below) consolidation of scores of atoms into triethylphosphine-coated NPs. The templating MOF, NU-1000, is characterized by mesoporous hexagonal channels (~31 Å diameter) and microporous triangular channels (~12 Å diameter). Also present, but not easily visualized via Scheme 1 alone, are apertures of ca. 8 Å width; these connect the various channels/pores and permit atoms and small molecules to move between them. The channel walls are defined by 1,3,6,8tetrakis(p-benzoate)pyrene, (TBAPy4−) linkers; their tetratopic nature almost certainly contributes to the stability of the MOF, especially in comparison to materials featuring ditopic linkers.39 Also contributing are comparatively strong Zr(IV)/oxy-anion bonds.40-42 Together the linkers and nodes create a csq-net topology. The synthesis of NU-1000,23 and its elaboration with phenylacetylene via SALI,43 were performed according to previously described procedures. NMR spectroscopy of the

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digested NU-1000-Acetylene sample showed the presence of 2.6 PA ligands per node

Scheme 1. Structure of NU-1000 ([Zr6(μ3-O)4(μ3−OH)4(OH)4(H2O)4(TBAPy)2]∞ with the linker and Zr6 node. Three post-synthetic modification reactions (PSM-1, -2, and -3) were performed on Zr6 node to obtain AuNPs templated and enshrouded by NU-1000 (NU1000-Au-nano). (Figure S1). In terms of MOF textural properties, the consequences of secondary ligand incorporation are decreases in apparent surface area (Brunauer–Emmett–Teller (BET) area) from 2250 to 1600 m2/g (Figure 1a) and DFT-(density functional theory)-calculated mesopore size from 30 to 23Å (Figure1b), with areas and sizes derived from reversible N2 adsorption isotherms. Single-crystal X– ray structure measurements show that the nonstructural, secondary ligands, i.e. PA ligands, are bound to the Zr6 node in monodentate (ester-like) fashion; see Figure 1c. The view in Figure 1e shows that the ligands extend into the MOF mesopores – consistent with the N2-isotherm-derived decrease in mesopore diameter.

Au(I) installation was accomplished by deprotonating the MOF’s pendant acetylene groups with potassium tert-butyloxide then substituting the chloride ligand of PEt3AuCl by the resulting phenylacetylide; see SI. Inductively-coupled-plasma opticalemission-spectroscopy (ICP-OES) measurements of NU-1000-AuPEt3 revealed an average loading of 1.4 ± 0.2 Au atoms and 1.4 ± 0.2 P atoms per Zr6 node. The matching gold and phosphorous loadings imply installation of Au-PEt3+ units, while Raman spectroscopy (Figure S2) indicates the presence of a gold acetylide fragment. Energy-dispersive X-ray spectroscopy (EDS) line-scan measurements show that Au and P are uniformly distributed through the


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Chemistry of Materials Figure 1. a) Nitrogen isotherms (77K), b) pore size distribution analysis of NU-1000, NU-1000-Acetylene, NU-1000-Au-PEt3; NU-1000Au-nano; c) and e) X-ray structure of NU-1000-Acetylene (100 K), (for clarity, only two PA orientations are shown); d) and f) DED maps showing the location of carboxy-phenylacetylene and Au-PEt3 in NU-1000-Acetylene and NU-1000-Au-PEt3, respectively. MOF; see Figure S3. Notably, in the absence of PA ligands, almost no gold is taken up (~0.04 Au/Zr6 from ICP-OES). N2 isotherms show a decrease in BET gravimetric surface area to 890 m2/g (Figure 1a); the change can be ascribed, in part, to an increase in MOF mass due to Au-PEt3+. More significant, however, is the decrease in area associated with loss of micropore (triangular pore) volume (Figure 1b). This observation suggests that grafted PAAu(I)PEt3 units detach and migrate into the triangular pores (or somehow contort sufficiently to extend into, and block, triangular pores).

separation distances expected based on face-centered-cubic (fcc) packing of gold atoms.32, 45

Consistent with this interpretation, difference envelope density (DED) analysis of synchrotron-derived x-ray diffraction data for NU-1000-Acetylene (i.e., relative to unmodified NU-1000) reveals extra electron density in the MOF mesopore (panel 1d). In contrast, but again consistent with pore-size data, DED data for NU-1000Au-PEt3 reveals extra electron density in the micropore (panel 1f). With Au(I)-functionalized NU-1000 in hand, we exposed the material for two hours at room temp. to a methanolic solution of NaBH4, a potent chemical reductant. As shown in Figure S5, the color of the functionalized MOF changes from yellow to dark brown. Such a change would be expected if isolated Au(I) atoms are converted Au(0) particles of sufficient size to display plasmon absorption in the visible spectrum; see also Figure S6. TEM measurements support the notion of AuNP formation, both within the MOF and to a modest extent on the MOF exterior – but only after exposure to reductant; see Figure S7. Au 4f XPS measurements showed that only upon NaBH4 treatment is Au(I) reduced; see Figure S8. ICP-OES assessments of the borohydride treated material (henceforth termed NU-1000-Au-nano) show that no gold is lost during the reduction, but that ~60% of the phosphorous is removed. As shown in Figure 1, partial removal of phosphine ligands and consolidation of Au atoms into particles results in partial recovery of MOF surface area and microporosity. Finally, powder X-ray diffraction measurements show that the initially prepared MOF remains crystalline through the modification process; see Figure S9. To gauge AuNP sizes we turned to pair-distribution function (PDF) analysis of total X-ray scattering (Synchrotron X-ray scattering results suitable for PDF analysis were collected at beamline 11-ID-B of the Advanced Photon Source at Argonne National Laboratory). We have used the PDF approach to good effect previously to gauge sizes MOF-templated and encapsulated copper nanoparticles.32 An attractive feature of the PDF approach is that it does not require long-range order, e.g. periodic siting of AuNPs and identical orientation of their lattices, in order to yield quantitative information about short-range ordering of atoms – such as atoms within metal nanoparticles. The black solid curve in Figure 2a shows the experimentally determined, differential pairdistribution function, G, versus distance, r, for NU-1000-Au-nano. (Here differential pair-distribution function means that contributions to G(r) from unmodified NU-1000 have been subtracted from the PDF of NU-1000-Au-nano). As peak intensities scale as the product of scattering cross-sections for pairs of atoms and as the number of such interactions, the differential PDF plot is dominated by peaks due to Au-Au, and to a lesser extent Au-Zr, interactions (i.e. interactions between atoms having large numbers of electrons). The intense peak at 2.8 Å is consistent with that expected from Au-Au nearest-neighbors (Figure S11).44 Also present are peaks corresponding to 2, 3, and 4X that distance, etc., depending on particle size, as well as peaks at other Au-Au

Figure 2. a) Differential pair distribution function, G, versus distance, r, for NU-1000-Au-nano. The observed G(r) (black, solid line) matches well with the calculated G(r) of two populations of AuNPs with diameters 1.5 and 3.7 nm (red, dashed line). DED maps viewed: b) parallel and c) perpendicular to the c-axis for NU1000-Au-nano. Note that most of the potential AuNP sites are empty (see text). The spatial distribution of filled sites, however, is random. Channel lengths (crystallite lengths, c direction) are roughly 5,000 nm. The view in image “b” reports on excess electron density appearing anywhere in a channel, and the image should not be interpreted to mean that the shown eight particles lie in the same plane (and likewise for the image in “c”). Data were fit to a model that approximates AuNP shapes as spherical (see below). As implied by the red dotted line in Figure 2, an excellent fit to the experimental results was obtained by allowing for two populations of AuNPs, each monodisperse. From the fit, the particle diameters are ~1.5 nm and ~3.7 nm, with each small particle consisting of ~100 gold atoms and each large particle consisting of ~1500 gold atoms. The fit indicates that ca. 78% of the gold atoms are organized in small NPs and ~22% in larger NPs. As such, ca. 98% of the AuNPs are ~1.5 nm in diameter and ca. 2% are ~3.7 nm. Notably, these diameters are similar to, albeit marginally larger than, the minimum diameters of NU-1000’s micropores and mesopores. The bottom sections of Figures 2 show DED data for the smaller AuNP. The particles clearly interact with the triangular-pore-defining tetraphenylpyrene linkers, are sited above and below ab planes passing through the MOF nodes. The occupancy of candidate channel sites by 1.5 nm AuNPs is about 1 in 60, while for 3.7 nm AuNPs it is roughly 1 in 3,000. (For simplicity we define a site as either one set of triangularly organized linkers or one set of hexagonally organized linkers, while recognizing that a 3.7 nm diameter particle would span (c direction) more than one hexagonal “site”.) We suggest that the observed low site occupancy, together with substantial London dispersion interactions between polarizable linkers and nanoparticles, NP siloing in individual channels, and possible physical entrapment enforced by the MOF nodes could serve to inhibit undesired NP sintering in catalysis applications. For our purposes, the most significant finding is that the pores of NU-1000 template and constrain the AuNP particle size, such that the sizes match those anticipated based on the widths of the pores/channels. Efforts to obtain similar particles using alternative



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acetylide-anchored precursors, such as chloro(dimethylsulfide)gold(I), were less successful in yielding channel-templated, size-constrained AuNPs.46 We speculate that the affinity of PEt3 for metallic gold serves to slow AuNP growth and prevent growth beyond the bounds of the initially present MOF channels, while also limiting migration of gold atoms to the MOF crystallite exterior. Given the somewhat unusual siting of 1.5 nm AuNPs on particle-encompassing aromatic hydrocarbon units, rather than more familiar metal-oxide or semimetal-oxide supports, we also examined in a preliminary way the binding of CO to the particle surfaces. The infrared-observable C=O stretching frequency of adsorbed carbon monoxide is often used as a reporter of local charge density at, and chemical composition of, metallic surfaces. As shown in Figure S12, exposure of NU-1000-Au-nano to CO at room temperature yields a DRIFTS peak at 2,043 cm-1 that is assignable as a C=O stretch for the gold-adsorbed probe. Subsequent exposure to flowing Ar (at room temperature) quickly eliminates the peak, implying comparatively weak binding of CO to Au – a conclusion not inconsistent with the presence of strongly adsorbed phosphine ligands. With the goal of removing PEt3, we subjected NU-1000-Aunano to heating in O2 at 200 oC, followed by heating in H2 at 200 oC; see SI for details. (ICP-OES measurements showed that the treatment removed about half the initially present phosphorous.) Exposure of treated samples to CO again yielded a peak at 2,043 cm-1, but also now a peak at 2,000 cm-1. Subsequent exposure to flowing Ar leads to a loss in intensity for the peak at 2,043 cm-1, but little or no change in the intensity of the peak at 2,000 cm-1. These frequencies are lower than typically observed for CO on AuNPs.47 It will be interesting to see how CO behaves once a reliable method has been devised for fully removing adsorbed phosphorous. Nevertheless, the results in hand, i.e. the observed CO frequencies, are suggestive of gold surfaces featuring greater electron density than is typical for AuNPs on conventional inorganic supports.18, 19 We have reported elsewhere that tetraphenylpyrene linkers in the Zr-based MOF, NU-901 (a polymorph of NU-1000), are sufficiently electron-donating to engender electronic conductivity when channel-doped with C60 as an electron acceptor.48 With well dispersed AuNPs within high-surface-area NU-1000 in hand, we examined their catalytic activity (5 mol% catalyst)49 for the hydrogenation of aqueous 4-nitrophenol (4-NP) to 4aminophenol (4-AP) by excess NaBH4, an oft-used test reaction for gauging the potential of specific forms of AuNPs as chemical catalysts.50 This reaction can be readily followed by monitoring the disappearance of a peak (λmax ≈ 400 nm) in the electronic absorption spectrum of 4-NP, and/or the growth of a peak (λmax ≈ 300 nm) due to 4-AP; see Figure 3a. Under these conditions (see SI for further details), the half-life for NU-1000-Au-nano catalyzed conversion of 4-NP to 4-AP is ~2 minutes. Figure 3b indicates pseudo-first order reaction kinetics. From the slope of the plot, the apparent rate constant is 4 x10-3 s-1. With the thermally treated version of the catalyst, where some but not all of the adsorbed phosphine, has been removed, the hydrogenation reaction is too fast to measure51 – underscoring the blocking or poisoning role played by the initially present phosphines. While hardly a comprehensive assessment of stability, we observed that MOF crystallinity is retained (Figure S15) and gold content is unchanged over the course of three recyclings of the catalyst (four cycles total). (See descriptions in SI and data in Figure S13.) A control experiment with gold-free NU-1000 yielded no observable hydrogenation (Figure S14).

Figure 3. a) Time dependent evolution of UV-Vis absorption spectra for the catalytic hydrogenation of 4-nitrophenol to 4aminophenol, and b) plot of ln (At) vs time (sec) to follow the kinetics of the reaction. At is the absorbance of 4-NP at 400 nm at time t (seconds). In summary, a zirconium based mesoporous MOF, NU-1000, has been employed as both a size-defining template and a support for AuNPs grown within the MOF via coordination of monometallic Au(I)phosphine complexes by nonstructural, nodeanchored phenylacetlylide ligands, followed by condensed-phase chemical reduction of Au(I) to Au(0). The neutral gold atoms, with phosphine ligands in tow, traverse the porous MOF and combine with other gold atoms to form gold nanoparticles. PDF analysis of data from synchrotron-facilitated total X-ray scattering shows that the particle size distribution is bimodal, with most NPs matching the width of NU-1000’s triangular micropores and a few (ca. 2%) matching the width of NU-1000’s hexagonal mesopores. These findings contrast with the more typical observation that the sizes of metal nanoparticles obtained by reducing and agglomerating MOFpore-infiltrating metal ions are unconstrained by the dimensions of the MOF pores.25, 29, 30 The PDF analysis additionally shows that the AuNPs are crystalline, with atoms organized in face-centeredcubic fashion. DED analysis shows that the particles are roughly spherical and that they are bounded by electron-rich, tetraphenylpyrene units, i.e. the organic component of NU-1000. In contrast to NU-1000 and NU-1000-Au-PEt3, the MOF-AuNP composite is catalytically competent for reduction (hydrogenation) of 4-nitrophenol to 4-aminophenol. Our focus, going forward, is on the introduction of surface-hydrated metal-oxide particles or clusters, immediately proximal to the templated AuNPs, as these may render AuNPs effective for activation of O2 and for selective oxidative catalysis.52 Finally, the quenching of MOF linker luminescence by AuNPs (Figure S6b) suggests possible applications in photocatalysis.

ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications website. Materials synthesis, characterization data and additional details (PDF).

AUTHOR INFORMATION Corresponding Authors * J. T. H. ([email protected]) * O. K. F. ([email protected])

Present Addresses † Institute for Integrated Cell-Material Sciences, Kyoto University, Japan


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Chemistry of Materials

‡ Department of Chemical Engineering, National Cheng Kung University, Taiwan

Notes The authors declare no competing financial interests.

ACKNOWLEDGMENTS We gratefully acknowledge support from the Defense Threat Reduction Agency (HDTRA1-18-1-0003). H. N. gratefully acknowledges support from the Ryan Fellowship program of the Northwestern University International Institute of Nanotechnology. L. R. gratefully acknowledges support from the U.S. Department of Energy (DOE), Office of Science, Office of Workforce Development for Teachers and Scientists, Office of Science Graduate Student Research (SCGSR) program. The SCGSR program is administered by the Oak Ridge Institute for Science and Education (ORISE) for the DOE. ORISE is managed by ORAU under Contract DE-SC0014664. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02- 06CH11357.

REFERENCES 1. Huang, X.; Jain, P. K.; El-Sayed, I. H.; El-Sayed, M. A., Gold Nanoparticles: Interesting Optical Properties and Recent Applications in Cancer Diagnostics and Therapy. Nanomedicine 2007, 2, 681-693. 2. Barnes, W. L.; Dereux, A.; Ebbesen, T. W., Surface Plasmon Subwavelength Optics. Nature 2003, 424, 824. 3. Ringe, E.; McMahon, J. M.; Sohn, K.; Cobley, C.; Xia, Y.; Huang, J.; Schatz, G. C.; Marks, L. D.; Van Duyne, R. P., Unraveling the Effects of Size, Composition, and Substrate on the Localized Surface Plasmon Resonance Frequencies of Gold and Silver Nanocubes: A Systematic Single-Particle Approach. J. Phys. Chem. C, 2010, 114, 12511-12516. 4. Camden, J. P.; Dieringer, J. A.; Zhao, J.; Van Duyne, R. P., Controlled Plasmonic Nanostructures for Surface-Enhanced Spectroscopy and Sensing. Acc. Chem. Res. 2008, 41, 1653-1661. 5. Kelly, K. L.; Coronado, E.; Zhao, L. L.; Schatz, G. C., The Optical Properties of Metal Nanoparticles: The Influence of Size, Shape, and Dielectric Environment. J. Phys. Chem. B, 2003, 107, 668-677. 6. Fan, J. A.; Wu, C.; Bao, K.; Bao, J.; Bardhan, R.; Halas, N. J.; Manoharan, V. N.; Nordlander, P.; Shvets, G.; Capasso, F., Self-Assembled Plasmonic Nanoparticle Clusters. Science 2010, 328, 1135-1138. 7. Kim, Y.; Johnson, R. C.; Hupp, J. T., Gold NanoparticleBased Sensing of “Spectroscopically Silent” Heavy Metal Ions. Nano Lett. 2001, 1, 165-167. 8. Mirkin, C. A.; Letsinger, R. L.; Mucic, R. C.; Storhoff, J. J., A DNA-Based Method for Rationally Assembling Nanoparticles into Macroscopic Materials. Nature 1996, 382, 607. 9. Yeh, Y.-C.; Creran, B.; Rotello, V. M., Gold Nanoparticles: Preparation, Properties, and Applications in Bionanotechnology. Nanoscale 2012, 4, 1871-1880. 10. Haruta, M., When Gold Is Not Noble: Catalysis by Nanoparticles. Chem. Rec. 2003, 3, 75-87. 11. Zhao, S.; Jin, R.; Jin, R., Opportunities and Challenges in Co2 Reduction by Gold- and Silver-Based Electrocatalysts: From Bulk Metals to Nanoparticles and Atomically Precise Nanoclusters. ACS Energy Lett 2018, 3, 452-462. 12. Daniel, M.-C.; Astruc, D., Gold Nanoparticles: Assembly, Supramolecular Chemistry, Quantum-Size-Related

Properties, and Applications toward Biology, Catalysis, and Nanotechnology. Chem. Rev. 2004, 104, 293-346. 13. Zhao, J.; Nguyen, S. C.; Ye, R.; Ye, B.; Weller, H.; Somorjai, G. A.; Alivisatos, A. P.; Toste, F. D., A Comparison of Photocatalytic Activities of Gold Nanoparticles Following Plasmonic and Interband Excitation and a Strategy for Harnessing Interband Hot Carriers for Solution Phase Photocatalysis. ACS Cent. Sci. 2017, 3, 482-488. 14. Panayotov, D. A.; Frenkel, A. I.; Morris, J. R., Catalysis and Photocatalysis by Nanoscale Au/Tio2: Perspectives for Renewable Energy. ACS Energy Letters 2017, 2, 1223-1231. 15. Valden, M.; Lai, X.; Goodman, D. W., Onset of Catalytic Activity of Gold Clusters on Titania with the Appearance of Nonmetallic Properties. Science 1998, 281, 1647-1650. 16. van Bokhoven, J. A.; Louis, C.; Miller, J. T.; Tromp, M.; Safonova, O. V.; Glatzel, P., Activation of Oxygen on Gold/Alumina Catalysts: In Situ High-Energy-Resolution Fluorescence and Time-Resolved X-Ray Spectroscopy. Angew. Chem. Int. Ed. 2006, 45, 4651-4654. 17. Hammer, B., Special Sites at Noble and Late Transition Metal Catalysts. Top. Catal. 2006, 37, 3-16. 18. Puértolas, B.; Mayoral, Á.; Arenal, R.; Solsona, B.; Moragues, A.; Murcia-Mascaros, S.; Amorós, P.; Hungría, A. B.; Taylor, S. H.; García, T., High-Temperature Stable Gold Nanoparticle Catalysts for Application under Severe Conditions: The Role of Tio2 Nanodomains in Structure and Activity. ACS Catal 2015, 5, 1078-1086. 19. Guzman, J.; Carrettin, S.; Corma, A., Spectroscopic Evidence for the Supply of Reactive Oxygen During Co Oxidation Catalyzed by Gold Supported on Nanocrystalline Ceo2. J. Am. Chem. Soc. 2005, 127, 3286-3287. 20. Lee, J.; Park, J. C.; Song, H., A Nanoreactor Framework of a Au@Sio2 Yolk/Shell Structure for Catalytic Reduction of PNitrophenol. Adv. Mater. 2008, 20, 1523-1528. 21. Haruta, M.; Yamada, N.; Kobayashi, T.; Iijima, S., Gold Catalysts Prepared by Coprecipitation for Low-Temperature Oxidation of Hydrogen and of Carbon Monoxide. J. Catal. 1989, 115, 301-309. 22. Haruta, M., Size- and Support-Dependency in the Catalysis of Gold. Catal. Today 1997, 36, 153-166. 23. Mondloch, J. E.; Bury, W.; Fairen-Jimenez, D.; Kwon, S.; DeMarco, E. J.; Weston, M. H.; Sarjeant, A. A.; Nguyen, S. T.; Stair, P. C.; Snurr, R. Q.; Farha, O. K.; Hupp, J. T., Vapor-Phase Metalation by Atomic Layer Deposition in a Metal–Organic Framework. J. Am. Chem. Soc. 2013, 135, 10294-10297. 24. Wang, T. C.; Vermeulen, N. A.; Kim, I. S.; Martinson, A. B. F.; Stoddart, J. F.; Hupp, J. T.; Farha, O. K., Scalable Synthesis and Post-Modification of a Mesoporous Metal-Organic Framework Called Nu-1000. Nat. Protoc 2015, 11, 149. 25. Luan, Y.; Qi, Y.; Gao, H.; Zheng, N.; Wang, G., Synthesis of an Amino-Functionalized Metal–Organic Framework at a Nanoscale Level for Gold Nanoparticle Deposition and Catalysis. J. Mater. Chem. A 2014, 2, 20588-20596. 26. Ishida, T.; Nagaoka, M.; Akita, T.; Haruta, M., Deposition of Gold Clusters on Porous Coordination Polymers by Solid Grinding and Their Catalytic Activity in Aerobic Oxidation of Alcohols. Chem. Eur. J 2008, 14, 8456-8460. 27. Esken, D.; Turner, S.; Lebedev, O. I.; Van Tendeloo, G.; Fischer, R. A., Au@Zifs: Stabilization and Encapsulation of Cavity-Size Matching Gold Clusters inside Functionalized Zeolite Imidazolate Frameworks, Zifs. Chem. Mater. 2010, 22, 6393-6401. 28. Gole, B.; Sanyal, U.; Mukherjee, P. S., A Smart Approach to Achieve an Exceptionally High Loading of Metal Nanoparticles Supported by Functionalized Extended Frameworks for Efficient Catalysis. Chem. Commun. 2015, 51, 4872-4875. 29. Hermes, S.; Schröter, M.-K.; Schmid, R.; Khodeir, L.; Muhler, M.; Tissler, A.; Fischer, R. W.; Fischer, R. A., Metal@Mof: Loading of Highly Porous Coordination Polymers


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Host Lattices by Metal Organic Chemical Vapor Deposition. Angew. Chem. Int. Ed. 2005, 44, 6237-6241. 30. Xu, H.; Li, Y.; Luo, X.; Xu, Z.; Ge, J., Monodispersed Gold Nanoparticles Supported on a Zirconium-Based Porous Metal–Organic Framework and Their High Catalytic Ability for the Reverse Water–Gas Shift Reaction. Chem. Commun. 2017, 53, 7953-7956. 31. Rungtaweevoranit, B.; Baek, J.; Araujo, J. R.; Archanjo, B. S.; Choi, K. M.; Yaghi, O. M.; Somorjai, G. A., Copper Nanocrystals Encapsulated in Zr-Based Metal–Organic Frameworks for Highly Selective Co2 Hydrogenation to Methanol. Nano Lett. 2016, 16, 7645-7649. 32. Platero-Prats, A. E.; Li, Z.; Gallington, L. C.; Peters, Aaron W.; Hupp, J. T.; Farha, O. K.; Chapman, K. W., Addressing the Characterisation Challenge to Understand Catalysis in Mofs: The Case of Nanoscale Cu Supported in Nu-1000. Faraday Discuss. 2017, 201, 337-350. 33. Volosskiy, B.; Niwa, K.; Chen, Y.; Zhao, Z.; Weiss, N. O.; Zhong, X.; Ding, M.; Lee, C.; Huang, Y.; Duan, X., MetalOrganic Framework Templated Synthesis of Ultrathin, WellAligned Metallic Nanowires. ACS Nano 2015, 9, 3044-3049. 34. Ke, F.; Zhu, J.; Qiu, L.-G.; Jiang, X., Controlled Synthesis of Novel Au@Mil-100(Fe) Core–Shell Nanoparticles with Enhanced Catalytic Performance. Chem. Commun. 2013, 49, 1267-1269. 35. Lu, G.; Li, S.; Guo, Z.; Farha, O. K.; Hauser, B. G.; Qi, X.; Wang, Y.; Wang, X.; Han, S.; Liu, X.; DuChene, J. S.; Zhang, H.; Zhang, Q.; Chen, X.; Ma, J.; Loo, S. C. J.; Wei, W. D.; Yang, Y.; Hupp, J. T.; Huo, F., Imparting Functionality to a Metal– Organic Framework Material by Controlled Nanoparticle Encapsulation. Nat. Chem 2012, 4, 310. 36. An, B.; Zhang, J.; Cheng, K.; Ji, P.; Wang, C.; Lin, W., Confinement of Ultrasmall Cu/Znox Nanoparticles in Metal– Organic Frameworks for Selective Methanol Synthesis from Catalytic Hydrogenation of Co2. J. Am. Chem. Soc. 2017, 139, 3834-3840. 37. Kim, I. S.; Li, Z.; Zheng, J.; Platero-Prats, A. E.; Mavrandonakis, A.; Pellizzeri, S.; Ferrandon, M.; Vjunov, A.; Gallington, L. C.; Webber, T. E.; Vermeulen, N. A.; Penn, R. L.; Getman, R. B.; Cramer, C. J.; Chapman, K. W.; Camaioni, D. M.; Fulton, J. L.; Lercher, J. A.; Farha, O. K.; Hupp, J. T.; Martinson, A. B. F., Sinter-Resistant Platinum Catalyst Supported by Metal– Organic Framework. Angew. Chem. Int. Ed. 2018, 57, 909-913. 38. Madrahimov, S. T.; Atesin, T. A.; Karagiaridi, O.; Sarjeant, A. A.; Farha, O. K.; Hupp, J. T.; Nguyen, S. T., Metal– Organic Frameworks Containing (Alkynyl)Gold Functionalities: A Comparative Evaluation of Solvent-Assisted Linker Exchange, De Novo Synthesis, and Post-Synthesis Modification. Cryst. Growth Des. 2014, 14, 6320-6324. 39. Howarth, A. J.; Liu, Y.; Li, P.; Li, Z.; Wang, T. C.; Hupp, J. T.; Farha, O. K., Chemical, Thermal and Mechanical Stabilities of Metal–Organic Frameworks. NAT. REV. MATER. 2016, 1, 15018. 40. Bai, Y.; Dou, Y.; Xie, L.-H.; Rutledge, W.; Li, J.-R.; Zhou, H.-C., Zr-Based Metal–Organic Frameworks: Design, Synthesis, Structure, and Applications. Chem. Soc. Rev. 2016, 45, 2327-2367. 41. Bon, V.; Senkovskyy, V.; Senkovska, I.; Kaskel, S., Zr(Iv) and Hf(Iv) Based Metal–Organic Frameworks with ReoTopology. Chem. Commun. 2012, 48, 8407-8409. 42. Cavka, J. H.; Jakobsen, S.; Olsbye, U.; Guillou, N.; Lamberti, C.; Bordiga, S.; Lillerud, K. P., A New Zirconium Inorganic Building Brick Forming Metal Organic Frameworks with Exceptional Stability. J. Am. Chem. Soc. 2008, 130, 1385013851. 43. Deria, P.; Bury, W.; Hupp, J. T.; Farha, O. K., Versatile Functionalization of the Nu-1000 Platform by Solvent-Assisted Ligand Incorporation. Chem. Commun. 2014, 50, 1965-1968.

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44. Consistent with initial installation of gold atoms as monometallic, acetylide-anchored complexes, the peak at 2.8 Å is absent the differential PDF plot for NU-1000-Au-PEt3 (Figure S11). 45. Kung, C.-W.; Audu, C. O.; Peters, A. W.; Noh, H.; Farha, O. K.; Hupp, J. T., Copper Nanoparticles Installed in Metal– Organic Framework Thin Films Are Electrocatalytically Competent for Co2 Reduction. ACS Energy Lett. 2017, 2, 23942401. 46. Voloskiy, et al. (ref. 32) report that under certain conditions where acetate is both a chemical reductant and a plausible facet-sensitive sorbate on metallic gold, HAuCl4 within MOF-545/PCN-222, can yield channel-templated metal rods. We were unable to extend this interesting approach to NU-1000. 47. Boccuzzi, F.; Chiorino, A., Ftir Study of Co Oxidation on Au/Tio2 at 90 K and Room Temperature. An Insight into the Nature of the Reaction Centers. J. Phys. Chem. B, 2000, 104, 54145416. 48. Goswami, S.; Ray, D.; Otake, K.-i.; Kung, C.-W.; Garibay, S. J.; Islamoglu, T.; Atilgan, A.; Cui, Y.; Cramer, C. J.; Farha, O. K.; Hupp, J. T., A Porous, Electrically Conductive HexaZirconium(Iv) Metal–Organic Framework. Chem. Sci. 2018, 9, 4477-4482. 49. For simplicity, the number of catalytic sites was equated with the total number of gold atoms present, rather than the (unknown) number of reactant-accessible gold atoms present. 50. Aditya, T.; Pal, A.; Pal, T., Nitroarene Reduction: A Trusted Model Reaction to Test Nanoparticle Catalysts. Chem. Commun. 2015, 51, 9410-9431. 51. Given the primitive rate measurement method employed here, we infer that the thermally treated version of the catalyst is, at a lower bound, an order-of-magnitude more active than the untreated version. 52. Saavedra, J.; Doan, H. A.; Pursell, C. J.; Grabow, L. C.; Chandler, B. D., The Critical Role of Water at the Gold-Titania Interface in Catalytic Co Oxidation. Science 2014, 345, 1599-1602.


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Pore-Templated Growth of Catalytically Active Gold Nanoparticles

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