Capping Ligands as Selectivity Switchers in Hydrogenation Reactions

Letter pubs.acs.org/NanoLett

Capping Ligands as Selectivity Switchers in Hydrogenation Reactions Soon Gu Kwon,† Galyna Krylova,† Aslihan Sumer,‡ Michael M. Schwartz,‡ Emilio E. Bunel,‡ Christopher L. Marshall,‡ Soma Chattopadhyay,§ Byeongdu Lee,§ Julius Jellinek,*,‡ and Elena V. Shevchenko*,† †

Center for Nanoscale Materials, ‡Chemical Sciences and Engineering Division, and §Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, United States. S Supporting Information *

ABSTRACT: We systematically investigated the role of surface modification of nanoparticles catalyst in alkyne hydrogenation reactions and proposed the general explanation of effect of surface ligands on the selectivity and activity of Pt and Co/Pt nanoparticles (NPs) using experimental and computational approaches. We show that the proper balance between adsorption energetics of alkenes at the surface of NPs as compared to that of capping ligands defines the selectivity of the nanocatalyst for alkene in alkyne hydrogenation reaction. We report that addition of primary alkylamines to Pt and CoPt3 NPs can drastically increase selectivity for alkene from 0 to more than 90% with ∼99.9% conversion. Increasing the primary alkylamine coverage on the NP surface leads to the decrease in the binding energy of octenes and eventual competition between octene and primary alkylamines for adsorption sites. At sufficiently high coverage of catalysts with primary alkylamine, the alkylamines win, which prevents further hydrogenation of alkenes into alkanes. Primary amines with different lengths of carbon chains have similar adsorption energies at the surface of catalysts and, consequently, the same effect on selectivity. When the adsorption energy of capping ligands at the catalytic surface is lower than adsorption energy of alkenes, the ligands do not affect the selectivity of hydrogenation of alkyne to alkene. On the other hand, capping ligands with adsorption energies at the catalytic surface higher than that of alkyne reduce its activity resulting in low conversion of alkynes. KEYWORDS: Nanoparticles, surface ligands, catalysis, selectivity, activity, binding energetics

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partial) of capping ligand molecules. Obviously, these adsorbed molecules can significantly impact the performance of nanocatalysts since catalytic reactions take place at surface, and ligands can affect the electronic characteristics of surface sites as well as hinder the access of the substrate molecules to the surface of NPs.42,43 At present, a clear understanding of the role of capping ligands in catalytic reactions, wherein chemically synthesized nanocatalysts are used, is still far from complete.44−47 Both moderate48−50 and reduced35,40,51,52 catalytic activities have been reported for surfactant-stabilized NPs. Surface molecules on colloidal NPs are usually remnants of chemical compounds introduced into reaction mixtures. Previously, it has been shown that modification of metal surfaces (e.g., Pt, Pd, and others) by the simple addition of strongly adsorbing chiral molecules allowed for efficient stereoselective control over reactions at the metal surface.53 Recently it has been also reported that surface modification of CoPt3 NPs by long-chain primary amines resulted in highly selective hydrogenation of CO bonds in α,β-unsaturated aldehydes.54 This finding has been attributed to the steric effect of the long-chain amines that

atalysis is a key step in production of various chemicals that has also a significant environmental aspect.1−7 The quest for “green chemistries” emphasizes the importance of catalysts with improved selectivity since they can reduce significantly the amount of the generated chemical waste.1 High-performance catalysts also play an important role in energy conversion and storage technologies. Significant progress has been made in the synthesis of highperformance nanocatalysts using solution-based approaches.8−22 Thus the specific activity of NPs can be greatly improved by the decrease in their size and by tuning their composition.23−34 It has also been shown that catalytically active NPs with certain shapes can dramatically affect the reaction pathways and change the selectivity of reactions.35−37 For example, Pt NPs with high-index facets prepared electrochemically showed very high catalytic activity in electro-oxidation of formic acid and ethanol.10 Also high surface-to-volume ratio of Pd−Pt nanodendrites was reported to lead to their enhanced electrocatalytic activity.28 Control of the size and shape of NPs is often achieved by the introduction of certain surfactant molecules that play a key role in synthesis of NPs.38−41 These molecules form complexes with the precursors and bind onto the surface of NPs affecting their nucleation and growth processes. As a result, the surface of the NPs synthesized in solution is covered by a layer (full or © 2012 American Chemical Society

Received: July 25, 2012 Revised: September 12, 2012 Published: September 18, 2012 5382

dx.doi.org/10.1021/nl3027636 | Nano Lett. 2012, 12, 5382−5388

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reactions were performed using a stainless steel reactor under 200 psig H2 (Supporting Information Figure S2). Hydrogenation of 4-octyne was chosen as a model catalytic reaction (Scheme 1). The desired product in our study is 4-octene and

favors adsorption of the substrate molecules to the NPs via the end aldehyde groups rather than adsorption of the CC bonds located in the middle of the molecule. The goal of this combined experimental/computational study is to examine and to understand the role of common capping ligands, such as primary amines, trioctylphosphine (TOP), trioctylphosphine oxide (TOPO), oleic acid, and others on the catalytic functionality of Pt and Co/Pt NPs in hydrogenation of alkynes. Selective hydrogenation of alkynes into alkenes has been an important topic in the study of catalytic hydrogenation reactions.55−63 Here we report that addition of primary alkylamines to Pt and CoPt3 NPs can drastically increase the selectivity for alkene from 0 to >90% without affecting the catalytic activity. We present a computational analysis for the observed experimental effects of the primary amine on the selectivity and activity of the NPs. We also provide the general explanation of the effect of surface modification of NPs on selectivity and conversion in hydrogenation of alkynes. In particular, we show that the source of these effects is the ligand coverage dependent difference in the adsorption energetics of the substrate molecules and the modifier ligands. We chose 3.5 nm Pt and 4.5 nm alloyed CoPt3 NPs (Figure 1a,b) as model catalysts based on good catalytic activity of Pt in

Scheme 1. Hydrogenation Reactions of 4-Octyne to 4Octene and Octane

selectivity is defined as the ratio [4-octene]/([4-octene] + [octane]). Thoroughly washed Pt and CoPt3 NPs showed high activity for hydrogenation reaction leading to the complete conversion of 4-octyne into octane meaning 0% selectivity for 4-octene (Figure 1c). However, the addition of primary alkylamine to the reaction mixture had a major effect on the reaction products. Thus, we observed that introduction of octylamine switched the selectivity for the desired 4-octene to a value greater than 90% and that the apparent conversion was at the same level as for purified NPs (∼99.9% conversion, Figure 1c). Among the isomers of 4-octene, the cis form was dominant in the product (Supporting Information Figure S3).67 Controlled experiments using 6 nm Co NPs and 1-octylamine showed zero activity for the alkyne hydrogenation reaction (Supporting Information Figure S4). Thus, the observed remarkable enhancement in the selectivity of Pt and CoPt3 nanocatalysts in the presence of octylamine was a consequence of surface modification of these NPs with octylamine. In the next experiments, we have added different capping ligands that are commonly used in the synthesis of NPs to 4octyne solutions containing purified 3.5 nm Pt NPs and monitored their effect on the catalytic performance. Addition of trioctylamine, oleic acid, and trioctylphosphine oxide (TOPO) affected neither the selectivity nor the activity as compared with the “clean” Pt NPs. Addition of trioctylphosphine (TOP) significantly lowered the activity, while 1-dodecanethiol (DDT) almost completely deactivated Pt NPs (Figure 2). The hydrogenation of alkynes proceeds through sequential addition of H2 to π-bonding orbitals of unsaturated hydrocarbons (Scheme 1). These reactions take place on the surfaces of the NP catalysts.68,69 The effect of octylamine shown in Figures 1 and 2 suggests that among various capping ligands tested,

Figure 1. TEM images of (a) 3.5 nm Pt and (b) 4.5 nm CoPt3 NPs; (c) composition of the reaction products formed as a result of 4octyne hydrogenation in the solutions containing only “clean” NPs and NPs with 0.13 M of 1-octylamine. The concentration of Pt was 2.6 ± 0.5 mM for both Pt and CoPt3 cases.

hydrogenation reactions.64 The Pt and CoPt3 NPs were synthesized according to slightly modified procedures described in refs 65 and 66, respectively. After synthesis, NPs were thoroughly purified by repeated washing and precipitation. According to thermogravimetric analysis (TGA), the amount of residual alkylamine ligand on purified Pt NPs was ∼4 wt % that corresponds to 0.1 mM in the hydrogenation reaction solution (Supporting Information Figure S1). The hydrogenation

Figure 2. Effect of different capping ligands on activity and selectivity of 3.5 nm Pt NPs in hydrogenation reaction of 4-octyne. The concentration of all ligands was ∼23 mM. 5383


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solution). Further increase in the octylamine concentration resulted in a rapid increase of selectivity that saturated at the octylamine concentration of ∼100 mM. The total level of conversion of 4-octyne was more than 99.9% at any concentration of octylamine. These data indicated that the selectivity was, indeed, defined by the degree of surface coverage with the amines (see Supporting Information Figure S5 for detail). Data supporting the central role of amine coverage are also presented in Figure 3b, which shows dependence of selectivity as a function of the amine concentration for four different concentrations of Pt NPs. In this experiment, the total (combined) surface area of Pt NPs changes from case to case by a factor of ∼2. Inspection of the graphs shows that four cases exhibit the same selectivity at amine concentrations that also differ from one case to another by a factor of ∼2. In other words, the amine concentrations that furnish a given level of selectivity are proportional to the total surface area of the NPs. The data in Figure 3a,b suggest that the high coverage of amine at the surface of NPs results in high selectivity for 4octene by blocking the hydrogenation of 4-octene to octane (Reaction 2 in Scheme 1). In order to test this idea, we carried out hydrogenation reactions of cis- and trans- forms of 4-octene as starting reagents. We observed that the increase in amine concentration results in the blocking of 4-octene hydrogenation into octane (Figure 3c) leaving nearly the same amount of 4octene as in the case of 4-octyne hydrogenation at the same concentrations of octylamine (Figure 3a). The relative amount of alkene after cis- or trans-4-octene hydrogenation was slightly (∼5%) higher than that from 4-octyne hydrogenation. This difference can be attributed to a small fraction of 4-octyne underwent a direct complete hydrogenation into 4-octane (cf. refs 55 and 56). The experimental data presented in Figure 3 provide a compelling evidence for the role of primary alkylamines as selectivity switchers/tuners. This role is to attenuate or even block almost completely the hydrogenation of 4-octene. In order to uncover the mechanism by which the amine ligands affect the selectivity in catalytic hydrogenation of alkynes, we performed density functional theory (DFT) studies of the energetics relevant to the processes at hand. In particular, we evaluated the adsorption energies of 4-octyne, cis-/trans-4octene, and octylamine on the same site of a clean and octylamine-covered (111) surface of Pt as represented by a 35atom Pt cluster (see Methodological Details and Supporting Information Figure S6 for details). The DFT computations showed that 4-octyne has the highest affinity to the clean surface of Pt while alkylamine has the lowest (Figure 4, Supporting Information Table S1). Figure 4 clearly shows that as the number of the coadsorbed octylamines increases, the adsorption energies of all four species decrease. Increasing the octylamine coverage on Pt surface reduces the adsorption energy of amines, alkenes, and alkynes due to the steric interactions between hydrocarbon chains. At all coverages, the adsorption energy of 4-octyne is higher than those of either form of 4-octene or octylamine. Notably, higher coverage of amine on the Pt surface affects the adsorption energy of CC double bonds the most (Figure 4a). At sufficiently high coverage of Pt surface with amines, the change in the order of adsorption energies tilts the competition between 4-alkenes and octylamines for binding sites on the catalyst surface in favor of amines (Figure 4a). At high concentrations of amine in the solution, the coverage of amine on the surface of the Pt NPs

primary alkylamines allow for Reaction 1 but block Reaction 2 (Scheme 1). In order to get a better understanding of the role of primary amines in alkyne hydrogenation catalyzed by Pt NPs we analyzed the effect of surface coverage of catalyst by the primary amines on selectivity. We gauged the degree of amine surface coverage by the concentration of the amines in the reaction mixture since there is a straightforward correlation between the concentrations of added amines and adsorbed at the surface of NPs. Thus, we have characterized the octylamine concentration dependence of selectivity (Figure 3a). The onset of selectivity starts at the octylamine concentration of ∼1−2 mM corresponding to a monolayer or slightly higher coverage of the NP surface with amines if all the added octylamine molecules would adsorb onto the NP surface (that is not necessarily the case since there is a dynamic equilibrium between octylamine molecules on the NP surface and in the

Figure 3. (a) Selectivity and conversion of 4-octyne hydrogenation at different concentrations of octylamine. The concentration of Pt was ∼3 mM. (b) Amine concentration-dependent selectivity for different [Pt]surf as indicated on the curves. (c) Composition of 4-octene in the product from trans-/cis-4-octene. Relative amount of alkene is defined as [alkene] normalized to the initial concentration of alkene or alkyne. In the inset, conversion for 4-octene hydrogenation is defined as 1-[4octene]final/[4-octene]initial. 5384


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Figure 5. Kinetic data demonstrating the conversion (upper section) and the selectivity (lower section) of 4-octyne hydrogenation using 3.5 nm Pt NPs as a function of octylamine concentration (shown on the right). The concentration of Pt was 2.6 ± 0.5 mM in all experiments. The data points shown in blue and red represent high and low selectivity regimes, respectively.

selectivities show a gradual decline with time. The rate of this decline decreases as the octylamine concentration increases (Figure 5) and this correlates with the decrease in the 4-octene adsorption energy as the octylamine coverage of the Pt nanocatalyst increases (Figure 4). Thus the theoretical calculations are in a very good agreement with the experimental results shown in Figures 3−5 and explain high selectivity and full conversion of alkynes at the surface of nanocatalysts densely covered with molecules of primary alkylamines. DFT calculations also indicate that the adsorption energetics of alkenes (CnH2n, n = 3, 4) as compared to that of amines defines hydrogenation selectivity. It was found that at high coverage of Pt surface with octylamine adsorption energies of 4octene and 3-hexene are lower than that of octylamine while 1octene has higher adsorption energy (Figure 6). As a result we can expect high yield of alkene in hydrogeneation reactions of 4-octyne and 3-hexyne and conversion of 1-octyne into octane. Indeed, experimentally, we observed selectivities greater than 80% from hydrogenation reactions of 3-hexyne, 4-octyne, and 5-decyne; however, selectivity of ∼4% was observed in case of 1-octyne hydrogenation (Figure 7). In order to provide further insights into selective exclusion of alkene from the surface of Pt NPs by the primary amines, we examined the effect of the hydrocarbon chain length of amine on the selectivity in 4-octyne hydrogenation reaction. The DFT calculations demonstrated that primary alkylamines with different chain lengths have approximately the same adsorption energy on Pt (Figure 8a) and, therefore, should have similar effect on selectivity. Our experiments corroborate this prediction. Experimentally, as in the case of octylamine, we observed the same high selectivity (in the range between ∼83 and 91%) for all studied primary alkylamines (Figure 8b). The DFT calculations also provide the rationale explanation for the observed low performance of trioctylamine as a selectivity promoter and for TOP being an activity attenuator (Figure 2). The calculated adsorption energy of trioctylamine on the Pt surface is 0.84 eV, which is lower than those of the primary amines, while the adsorption energy of TOP is 2.55 eV, which is higher than that of even 4-octyne. The lower adsorption energy of trioctylamine makes it a less favorable candidate for substitution of 4-octene. The high adsorption energy of TOP makes it a poison for catalyst. These findings

Figure 4. (a) Plots of the adsorption energies of 4-octyne, cis-4octene, trans-4-octene, and 1-octylamine on clean and 1-octylamine decorated (111) Pt surface (35 atom cluster) as a function of octylamine coverage. Adsorption energies were obtained from DFT computation. Dash red circle highlights the difference in the Eads of 4octene and octylamine. (b) Depiction of the structures used in DTF calculations.

increases so that the adsorption energy of amines becomes higher than those of alkene and, as a result, impedes the adsorption of alkene molecules, blocking the conversion of 4octene into octane (Scheme 1). On the other hand, the adsorption energy of 4-octyne is still substantially higher than those of primary amine even at the high coverage of amine and, hence, the hydrogenation of 4-octyne to 4-octene is not impeded at any amine concentration. The coverage-dependent trends and changes in the adsorption energies of substrates and capping ligands provide the rational for understanding the role of primary amines as selectivity switchers in catalytic hydrogenation on Pt nanoparticles. The presented picture is also consistent with the results of our kinetic measurements shown in Figure 5. The activity (conversion of 4-octyne) is ∼99.9% over all time scales considered. The selectivity, however, exhibits different patterns of time-dependence at different amine concentrations. At the lowest concentration of octylamine (0.1 mM), the selectivity of ∼45% at t = 15 min drops to 0% at t = 30 min meaning that all 4-octyne is converted into octane. At the highest amine concentration (210 mM), the selectivity is above 90% and negligibly changes with time. This is consistent with the displacement of all 4-octenes from the catalyst surface by octylamines as soon as 4-octenes are generated from 4-octynes. At intermediate octylamine concentrations, the initial high 5385


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Figure 6. Summary of the DFT calculations on the effect of position of CC bond on the adsorption energy.

hydrogen as reactants, and alkylamines, oleic acid, trioctylphosphine, and trioctylphosphine oxide as capping ligands, we show that the balance between the adsorption energetics of substrates and capping ligands determines the selectivity and activity of catalyst. A judicious selection of capping ligands with appropriate adsorption energies on catalyst can lead to a remarkable enhancement in its selectivity. We demonstrate that sufficient concentrations of primary alkylamine ligands result in higher than 90% selectivity toward selective hydrogenation at an overall activity of 99.9%. Capping ligands with too low adsorption energies, as compared to those of the subtrates, have little or no effect on selectivity. Capping ligands with too high adsorption energies significantly reduce activity. We expect the general findings and methodology of this study to become an efficient tool in rational use of capping ligands as modifiers of catalytic functionality at the nanoscale. Methodological Details. Synthesis of NPs. The synthesis of Pt NPs was carried out by a method described in ref 65 with minor modification. A reaction mixture was prepared by adding 0.2 g of Pt(acac)2, 0.89 g of oleic acid, and 0.81 g of oleylamine into 10 mL of 1-octadecene. It was degassed at 100 °C for 20 min and heated at 120 °C for 30 min under nitrogen atmosphere to form a clear yellow solution. It was further heated to 200 °C at the rate of 4 °C/min and then kept at that temperature for 30 min. After the reaction was stopped, Pt NPs were separated and washed with excess acetone two times. CoPt3 NPs were synthesized following the methods from ref 66. Catalytic Studies. The hydrogenation reaction was carried out in a stainless steel reactor at room temperature for 3 h under H2 atmosphere (200 psig). In a standard condition, the

Figure 7. Selectivity in hydrogenation reactions of different alkyne molecules. All reactions were carried out with the fixed concentration of 1-octylamine at 39 mM using 3.5 nm Pt NPs. The concentration of P was 2.6 ± 0.5 mM.

and considerations point to the importance of adsorption energy as a guiding parameter for a judicious selection of capping ligands with desired activity and selectivity effects. In summary, this combined experimental/computational study addresses the general subject of capping ligands as modifiers of catalytic functionality of nanoparticles and presents a methodology for understanding the role of surface modification in defining/affecting the catalysts’ activity and/or selectivity. In particular, we emphasize the role of capping ligands as a means for substantial enhancement of selectivity. Using Pt and CoPt3 NPs as catalysts, hydrocarbons and

Figure 8. (a) Summary of the DFT calculations on the adsorption energy of primary alkylamines. (b) The effect of the carbon chain length in primary amines on the selectivity in 4-octyne hydrogenation reaction using 3.5 nm Pt NPs. C6, C8, C12, and C18 are abbreviations for 1-hexyl-, 1octyl-, 1-dodecyl-, and 1-octadecylamine, respectively. The concentrations of amines were 39 mM. The concentration of Pt was 2.6 ± 0.5 mM. 5386


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Notes

reaction solution was prepared by dispersing Pt nanoparticles in 1.0 mL dodecane containing 3.75 wt % (255 mM) of 4-octyne. The amount of Pt in the solution was controlled in the range of 0.4−0.6 mg, which was confirmed by inductively coupled plasma (ICP) analysis. [Pt]surf is defined as the concentration of Pt atoms at the surface of Pt NPs in the solution. The value of [Pt]surf is calculated based on the net amount of Pt atoms in the solution and the size of Pt NPs from TEM. During the reaction, the solution was stirred at ∼7000 rpm. After the reaction, the solutions were purged with nitrogen to remove any residual hydrogen. Otherwise stated, the concentration of amine in the reaction solution was controlled by adding 1-octylamine. On the basis of the composition data from the reaction product, conversion and selectivity of the catalytic reaction of 4-octyne are defined as follow: (Conversion) = 1 − [4-octyne]/[4octyne]initial; (Selectivity) = [4-octene]/([4-octene] + [octane]). Characterization. Samples for transmission electron microscopy (TEM) were prepared by dropping and drying of 1−2 μL of toluene solution of NPs on a carbon-coated copper grid (Ted Pella). TEM measurements were performed using a JEOL 2100F microscope operated at 200 kV. Thermogravimetric analysis was carried out using a Mettler Toledo TGA/ SDTA851e instrument. The sample was heated from 25 to 600 °C at the heating rate of 3 °C/min. The composition of the solution after hydrogenation reaction was analyzed by gas chromatography−mass spectrometry (GC-MS) instrument composed of an Agilent 6890 GC system and a 5973 Network Selective Detector. Computational Framework. The computations were performed within density functional theory with the PBE exchange-correlation functional, double-ζ basis sets, and Goedecker−Teter−Hutter type pseudopotentials as implemented in the CP2K package.70 The size of the computation cell was 30 × 30 × 30 Å. The adsorption energies were computed using Supporting Information equations S3 and S4.

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The authors declare no competing financial interest.

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ACKNOWLEDGMENTS Use of the Center for Nanoscale Materials was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC0206CH11357 (S.G.K., G.K., E.V.S.). This work was also supported by the Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences, U.S. Department of Energy under Contract No. DE-AC02-06CH11357 (M.M.S., E.E.B., S.C., B.L., J.J.), and by the Institute for Atomefficient Chemical Transformations (IACT), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences (A.S., C.L.M., J.J.).

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(1) Grunes, J.; Zhuab, J.; Somorjai, G. A. Chem. Commun. 2003, 2257−2260. (2) Somorjai, G. A.; Contreras, A. M.; Montano, M.; Rioux, R. M. Proc. Natl. Acad. Sci. U.S.A. 2006, 103, 10577−10583. (3) Xiong, Y.; Wiley, B. J.; Xia, Y. Angew. Chem., Int. Ed. 2007, 46, 7157−7159. (4) Astruc, D.; Lu, F.; Aranzaes, J. R. Angew. Chem., Int. Ed. 2005, 44, 7852−7872. (5) Roucoux, A.; Schulz, J.; Patin, H. Chem. Rev. 2002, 102, 3757− 3778. (6) Jia, C. J.; Schüth, F. Phys. Chem. Chem. Phys. 2011, 13, 2457− 2487. (7) Somorjai, G. A.; Li, Y. Top. Catal. 2010, 53, 832−847. (8) Sun, Y.; Xia, Y. Science 2002, 298, 2176−2179. (9) Xiong, Y.; Cai, H.; Wiley, B. J.; Wang, J.; Kim, M. J.; Xia, Y. J. Am. Chem. Soc. 2007, 129, 3665−3675. (10) Tian, N.; Zhou, Z. Y.; Sun, S. G.; Ding, Y.; Wang, Z. L. Science 2007, 316, 732−735. (11) Xiong, Y.; Xia, Y. Adv. Mater. 2007, 19, 3385−3391. (12) Lim, B.; Xiong, Y.; Xia, Y. Angew. Chem., Int. Ed. 2007, 46, 9279−9282. (13) Yamada, Y.; Tsung, C. K.; Huang, W.; Huo, Z.; Habas, S. E.; Soejima, T.; Aliaga, C. E.; Somorjai, G. A.; Yang, P. Nature Chem. 2011, 3, 372−376. (14) George, C.; Dorfs, D.; Bertoni, G.; Falqui, A.; Genovese, A.; Pellegrino, T.; Roig, A.; Quarta, A.; Comparelli, R.; Curri, M. L.; Cingolani, R.; Manna, L. J. Am. Chem. Soc. 2011, 133, 2205−2217. (15) Sanlés-Sobrido, M.; Pérez-Lorenzo, M.; Rodríguez-González, B.; Salgueiriño, V.; Correa-Duarte, M. A. Angew. Chem., Int. Ed. 2012, 51, 3877−3882. (16) Jin, M.; Zhang, H.; Xie, Z.; Xia, Y. Angew. Chem., Int. Ed. 2011, 50, 7850−7854. (17) Yu, T.; Kim, D. Y.; Zhang, H.; Xia, Y. Angew. Chem., Int. Ed. 2011, 50, 2773−2777. (18) Witham, C. A.; Huang, W.; Tsung, C. K.; Kuhn, J. N.; Somorjai, G. A.; Toste, F. D. Nature Chem. 2010, 2, 36−41. (19) Huang, W.; Liu, J. H. C.; Alayoglu, P.; Li, Y.; Witham, C. A.; Tsung, C. K.; Toste, F. D.; Somorjai, G. A. J. Am. Chem. Soc. 2010, 132, 16771−16773. (20) Lim, B.; Xia, Y. Angew. Chem., Int. Ed. 2011, 50, 76−85. (21) Kim, S. W.; Park, J.; Jang, Y.; Chung, Y.; Hwang, S.; Hyeon, T.; Kim, Y. W. Nano Lett. 2003, 3, 1289−1291. (22) Son, S. U.; Jang, Y.; Park, J.; Na, H. B.; Park, H. M.; Yun, H. J.; Lee, J.; Hyeon, T. J. Am. Chem. Soc. 2004, 126, 5026−5027. (23) Xu, Z.; Xiao, F. S.; Purnell, S. K.; Alexeev, O.; Kawi, S.; Deutsch, S. E.; Gates, B. C. Nature 1994, 372, 346−348. (24) Lee, H.; Habas, S. E.; Somorjai, G. A.; Yang, P. J. Am. Chem. Soc. 2008, 130, 5406−5407.

ASSOCIATED CONTENT

S Supporting Information *

TGA data on washed Pt NPs (Figure S1); a photo of a stainless steel hydrogenation reactor (Figure S2); chromatogram of the product from 4-octyne hydrogenation reaction (Figure S3); composition data of the product from 4-octyne hydrogenation reactions using Co NPs and 1-octylamine in the place of catalyst (Figure S4); DFT calculation data for the adsorption energies of 4-octyne, cis-4-octene, trans-4-octene, and 1octylamine on clean Pt surface and 4- and 5-amine decorated Pt surfaces (Table S1); DFT calculation data for the adsorption energies of different types of ligands on clean Pt surface (Table S2); competitive adsorption model theory for competitive binding of 4-octene and 1-octylamine onto the surface of Pt NPs (Figure S5); EXAFS measurements data on CoPt3 NPs before and after catalytic reactions (Tables S3 and S4); computational methodology and Pt35 cluster model (Figure S6). This material is available free of charge via the Internet at http://pubs.acs.org.

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REFERENCES

AUTHOR INFORMATION

Corresponding Author

*Tel: +1-630-252-3463. Fax: +1-630-252-7633. E-mail: (J.J.) [email protected]; (E.V.S.) [email protected]. 5387


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(25) Grabow, L. C.; Mavrikakis, M. Angew. Chem., Int. Ed. 2008, 47, 7390−7392. (26) Tsung, C. K.; Kuhn, J. N.; Huang, W.; Aliaga, C.; Hung, L. I.; Somorjai, G. A.; Yang, P. J. Am. Chem. Soc. 2009, 131, 5816−5822. (27) Tao, F.; Grass, M. E.; Zhang, Y.; Butcher, D. R.; Renzas, J. R.; Liu, Z.; Chung, J. Y.; Mun, B. S.; Salmeron, M.; Somorjai, G. A. Science 2008, 322, 932−934. (28) Lim, B.; Jiang, M.; Camargo, P. H. C.; Cho, E. C.; Tao, J.; Lu, X.; Zhu, Y.; Xia, Y. Science 2009, 324, 1302−1305. (29) Shang, C.; Liu, Z. P. J. Am. Chem. Soc. 2011, 133, 9938−9947. (30) Zhang, Y.; Cui, X.; Shi, F.; Deng, Y. Chem. Rev. 2012, 112, 2467−2505. (31) Chang, L. Y.; Barnard, A. S.; Gontard, L. C.; Dunin-Borkowski, R. E. Nano Lett. 2010, 10, 3073−3076. (32) Zhang, H.; Jin, M.; Wang, J.; Li, W.; Camargo, P. H. C.; Kim, M. J.; Yang, D.; Xie, Z.; Xia, Y. J. Am. Chem. Soc. 2011, 133, 6078−6089. (33) Guo, S.; Sun, S. J. Am. Chem. Soc. 2012, 134, 2492−2495. (34) Zhang, G. R.; Zhao, D.; Feng, Y. Y.; Zhang, B.; Su, D. S.; Liu, G.; Xu, B. Q. ACS Nano 2012, 6, 2226−2236. (35) Narayanan, R.; El-Sayed, M. A. J. Phys. Chem. B 2005, 109, 12663−12676. (36) Zhang, Y.; Grass, M. E.; Kuhn, J. N.; Tao, F.; Habas, S. E.; Huang, W.; Yang, P.; Somorjai, G. A. J. Am. Chem. Soc. 2008, 130, 5868−5869. (37) Lee, I.; Delbecq, F.; Morales, R.; Albiter, M. A.; Zaera, F. Nature Mater. 2009, 8, 132−138. (38) Rogach, A. L.; Talapin, D. V.; Shevchenko, E. V.; Kornowski, A.; Haase, M.; Weller, H. Adv. Funct. Mater. 2002, 12, 653−664. (39) Park, J.; Joo, J.; Kwon, S. G.; Jang, Y.; Hyeon, T. Angew. Chem., Int. Ed. 2007, 46, 4630−4660. (40) Mazumder, V.; Sun, S. J. Am. Chem. Soc. 2009, 131, 4588−4589. (41) Niu, Z.; Peng, Q.; Gong, M.; Rong, H.; Li, Y. Angew. Chem., Int. Ed. 2011, 50, 6315−6319. (42) Gonza lez-Ga lvez, D.; Nolis, P.; Philippot, K.; Chaudret, B.; Leeuwen, P. W. N. M. v. ACS Nano 2012, 2, 317−321. (43) Iablokov, V.; Beaumont, S. K.; Alayoglu, S.; Pushkarev, V. V.; Specht, C.; Gao, J.; Alivisatos, A. P.; Kruse, N.; Somorjai, G. A. Nano Lett. 2012, 12, 3091−3096. (44) Stowell, C. A.; Korgel, B. A. Nano Lett. 2005, 5, 1203−1207. (45) Lara, P.; Rivada-Wheelaghan, O.; Conejero, S.; Poteau, R.; Philippot, K.; Chaudret, B. Angew. Chem., Int. Ed. 2011, 50, 12080− 12084. (46) Marshall, S. T.; O’Brien, M.; Oetter, B.; Corpuz, A.; Richards, R. M.; Schwartz, D. K.; Medlin, J. W. Nature Mater. 2010, 9, 853−858. (47) Moreno, M.; Ibañez, F. J.; Jasinski, J. B.; Zamborini, F. P. J. Am. Chem. Soc. 2011, 133, 4389−4397. (48) Borchert, H.; Fenske, D.; Kolny-Olesiak, J.; Parisi, J.; AlShamery, K.; Bäumer, M. Angew. Chem., Int. Ed. 2007, 46, 2923−2926. (49) Bratlie, K. M.; Lee, H.; Komvopoulos, K.; Yang, P.; Somorjai, G. A. Nano Lett. 2007, 7, 3097−3101. (50) Jürgens, B.; Borchert, H.; Ahrenstorf, K.; Sonström, P.; Pretorius, A.; Schowalter, M.; Gries, K.; Zielasek, V.; Rosenauer, A.; Weller, H.; Bäumer, M. Angew. Chem., Int. Ed. 2008, 47, 8946−8949. (51) Li, Y.; El-Sayed, M. A. J. Phys. Chem. B 2001, 105, 8938−8943. (52) Lee, H.; Habas, S. E.; Kweskin, S.; Butcher, D.; Somorjai, G. A.; Yang, P. Angew. Chem., Int. Ed. 2006, 45, 7824−7828. (53) Mallat, T.; Orglmeister, E.; Baiker, A. Chem. Rev. 2007, 107, 4863−4890. (54) Wu, B.; Huang, H.; Yang, J.; Zheng, N.; Fu, G. Angew. Chem., Int. Ed. 2012, 51, 3440−3443. (55) Al-Ammar, A. S.; Webb, G. J. Chem. Soc. 1979, 75, 1900−1911. (56) Molnár, Á .; Sárkány, A.; Varga, M. J. Mol. Catal. A 2001, 173, 185−221. (57) Kim, W. J.; Moon, S. H. Catal. Today 2012, 185, 2−16. (58) Studt, F.; Abild-Pedersen, F.; Bligaard, T.; Sørensen, R. Z.; Christensen, C. H.; Nørskov, J. K. Science 2008, 320, 1320−1322. (59) Teschner, D.; Vass, E.; Hävecker, M.; Zafeiratos, S.; Schnörch, P.; Sauer, H.; Knop-Gericke, A.; Schlögl, R.; Chamam, M.; Wootsch,

A.; Canning, A. S.; Gamman, J. J.; Jackson, S. D.; McGregor, J.; Gladden, L. F. J. Catal. 2006, 242, 26−37. (60) Jackson, S. D.; Hamilton, C. A.; Kelly, G. J.; Bruin, D. d. React. Kinet. Catal. Lett. 2001, 73, 77−82. (61) Anderson, J. A.; Mellor, J.; Wells, R. P. K. J. Catal. 2009, 261, 208−216. (62) Chen, B.; Dingerdissen, U.; Krauter, J. G. E.; Rotgerink, H. G. J. L.; Möbus, K.; Ostgard, D. J.; Panster, P.; Riermeier, T. H.; Seebald, S.; Tacke, T.; Trauthwein, H. Appl. Catal., A 2005, 280, 17−46. (63) Dobrovolná, Z.; Ka, P. J. Mol. Catal. A 1998, 130, 279−284. (64) Zaera, F.; Somorjai, G. A. J. Am. Chem. Soc. 1984, 106, 2288− 2293. (65) Wang, C.; Daimon, H.; Lee, Y.; Kim, J.; Sun, S. J. Am. Chem. Soc. 2007, 129, 6974−6975. (66) Shevchenko, E. V.; Talapin, D. V.; Rogach, A. L.; Kornowski, A.; Haase, M.; Weller, H. J. Am. Chem. Soc. 2002, 124, 11480−11485. (67) Delbecq, F.; Zaera, F. J. Am. Chem. Soc. 2008, 130, 14924− 14925. (68) Delbecq, F.; Sautet, P. Catal. Lett. 1994, 28, 89−98. (69) Sautet, P.; Paul, J. F. Catal. Lett. 1991, 9, 245−260. (70) VandeVondele, J.; Krack, M.; Mohamed, F.; Parrinello, M.; Chassaing, T.; Hutter, J. Comput. Phys. Commun. 2005, 167, 103−128.

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